🕷️ Crawler Inspector

URL Lookup

Direct Parameter Lookup

Raw Queries and Responses

1. Shard Calculation

Query:

Response:

Calculated Shard: 53 (from laksa187)

2. Crawled Status Check

Query:

curl -X POST \
  'http://laksa053.int.ahrefs:8124/' \
  -H 'Content-Type: text/plain' \
  -H 'X-ClickHouse-Database: crawler3' \
  -H 'Authorization: Basic YXBpOg==' \
  -d 'SELECT getAhrefsURLFromUnparsed(src_unparsed) AS found_url, ifNull(toUnixTimestamp(download_stamp), 0) AS crawl_time, ifNull(toUnixTimestamp(props_url_first_seen), 0) AS first_indexed_time, download_http_code AS http_code, src_unparsed AS src_unparsed, src_root_hash AS src_root_hash, history_drop_reason AS history_drop_reason, meta_title AS meta_title, meta_descriptions AS meta_descriptions, attrs_boilerpipe_text AS attrs_boilerpipe_text, attrs_markdown AS attrs_markdown, attrs_readable_markdown AS attrs_readable_markdown, meta_canonical AS meta_canonical FROM crawler3.page_info_local FINAL PREWHERE (src_root_hash, src_unparsed) IN ((getAhrefsRootHashFromUnparsed(getAhrefsUnparsedNoserviceFromURL(\'https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control\')), getAhrefsUnparsedNoserviceFromURL(\'https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control\'))) FORMAT JSONEachRow'

Response:

{"found_url":"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control","crawl_time":1775904613,"first_indexed_time":1741914435,"http_code":200,"src_unparsed":"org,mozilla!developer,\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control s443","src_root_hash":"7082249407640205653","history_drop_reason":null,"meta_title":"Cache-Control header - HTTP | MDN","meta_descriptions":["The HTTP Cache-Control header holds directives (instructions) in both requests and responses that control caching in browsers and shared caches (e.g., Proxies, CDNs)."],"attrs_boilerpipe_text":"Syntax\nhttp\nCache-Control: <directive>, <directive>, ...\nCache directives follow these rules:\nCaching directives are case-insensitive. However, lowercase is recommended because some implementations do not recognize uppercase directives.\nMultiple directives are permitted and must be comma-separated (e.g.,\nCache-control: max-age=180, public\n).\nSome directives have an optional argument. When an argument is provided, it is separated from the directive name by an equals symbol (\n=\n). Typically, arguments for the directives are integers and are therefore not enclosed in quote characters (e.g.,\nCache-control: max-age=12\n).\nCache directives\nThe following table lists the standard\nCache-Control\ndirectives:\nRequest\nResponse\nmax-age\nmax-age\nmax-stale\n-\nmin-fresh\n-\n-\ns-maxage\nno-cache\nno-cache\nno-store\nno-store\nno-transform\nno-transform\nonly-if-cached\n-\n-\nmust-revalidate\n-\nproxy-revalidate\n-\nmust-understand\n-\nprivate\n-\npublic\n-\nimmutable\n-\nstale-while-revalidate\nstale-if-error\nstale-if-error\nNote: Check the\ncompatibility table\nfor their support; user agents that don't recognize them should ignore them.\nVocabulary\nThis section defines the terms used in this document, some of which are from the specification.\n(HTTP) cache\nImplementation that holds requests and responses for reusing in subsequent requests. It can be either a shared cache or a private cache.\nShared cache\nCache that exists between the origin server and clients (e.g., Proxy, CDN). It stores a single response and reuses it with multiple users — so developers should avoid storing personalized contents to be cached in the shared cache.\nPrivate cache\nCache that exists in the client. It is also called\nlocal cache\nor\nbrowser cache\n. It can store and reuse personalized content for a single user.\nStore response\nStore a response in caches when the response is cacheable. However, the cached response is not always reused as-is. (Usually, \"cache\" means storing a response.)\nReuse response\nReuse cached responses for subsequent requests.\nRevalidate response\nAsk the origin server whether or not the stored response is still\nfresh\n. Usually, the revalidation is done through a conditional request.\nFresh response\nIndicates that the response is\nfresh\n. This usually means the response can be reused for subsequent requests, depending on request directives.\nStale response\nIndicates that the response is a\nstale response\n. This usually means the response can't be reused as-is. Cache storage isn't required to remove stale responses immediately because revalidation could change the response from being stale to being\nfresh\nagain.\nAge\nThe time since a response was generated. It is a criterion for whether a response is\nfresh or stale\n.\nDirectives\nThis section lists directives that affect caching — both response directives and request directives.\nResponse Directives\nmax-age\nThe\nmax-age=N\nresponse directive indicates that the response remains\nfresh\nuntil\nN\nseconds after the response is generated.\nhttp\nCache-Control: max-age=604800\nIndicates that caches can store this response and reuse it for subsequent requests while it's\nfresh\n.\nNote that\nmax-age\nis not the elapsed time since the response was received; it is the elapsed time since the response was generated on the origin server.\nSo if the other cache(s) — on the network route taken by the response — store the response for 100 seconds (indicated using the\nAge\nresponse header field), the browser cache would deduct 100 seconds from its\nfreshness lifetime\n.\nIf the\nmax-age\nvalue is negative (for example,\n-1\n) or isn't an integer (for example,\n3599.99\n), then the caching behavior is unspecified. Caches are encouraged to treat the value as if it were\n0\n(this is noted in the\nCalculating Freshness Lifetime\nsection of the HTTP specification).\nhttp\nCache-Control: max-age=604800\nAge: 100\ns-maxage\nThe\ns-maxage\nresponse directive indicates how long the response remains\nfresh\nin a shared cache.\nThe\ns-maxage\ndirective is ignored by private caches, and overrides the value specified by the\nmax-age\ndirective or the\nExpires\nheader for shared caches, if they are present.\nhttp\nCache-Control: s-maxage=604800\nno-cache\nThe\nno-cache\nresponse directive indicates that the response can be stored in caches, but the response must be validated with the origin server before each reuse, even when the cache is disconnected from the origin server.\nhttp\nCache-Control: no-cache\nIf you want caches to always check for content updates while reusing stored content,\nno-cache\nis the directive to use. It does this by requiring caches to revalidate each request with the origin server.\nNote that\nno-cache\ndoes not mean \"don't cache\".\nno-cache\nallows caches to store a response but requires them to revalidate it before reuse. If the sense of \"don't cache\" that you want is actually \"don't store\", then\nno-store\nis the directive to use.\nmust-revalidate\nThe\nmust-revalidate\nresponse directive indicates that the response can be stored in caches and can be reused while\nfresh\n. If the response becomes\nstale\n, it must be validated with the origin server before reuse.\nTypically,\nmust-revalidate\nis used with\nmax-age\n.\nhttp\nCache-Control: max-age=604800, must-revalidate\nHTTP allows caches to reuse\nstale responses\nwhen they are disconnected from the origin server.\nmust-revalidate\nis a way to prevent this from happening - either the stored response is revalidated with the origin server or a 504 (Gateway Timeout) response is generated.\nproxy-revalidate\nThe\nproxy-revalidate\nresponse directive is the equivalent of\nmust-revalidate\n, but specifically for shared caches only.\nno-store\nThe\nno-store\nresponse directive indicates that any caches of any kind (private or shared) should not store this response.\nhttp\nCache-Control: no-store\nprivate\nThe\nprivate\nresponse directive indicates that the response can be stored only in a private cache (e.g., local caches in browsers).\nhttp\nCache-Control: private\nYou should add the\nprivate\ndirective for user-personalized content, especially for responses received after login and for sessions managed via cookies.\nIf you forget to add\nprivate\nto a response with personalized content, then that response can be stored in a shared cache and end up being reused for multiple users, which can cause personal information to leak.\npublic\nThe\npublic\nresponse directive indicates that the response can be stored in a shared cache. Responses for requests with\nAuthorization\nheader fields must not be stored in a shared cache; however, the\npublic\ndirective will cause such responses to be stored in a shared cache.\nhttp\nCache-Control: public\nIn general, when pages are under Basic Auth or Digest Auth, the browser sends requests with the\nAuthorization\nheader. This means that the response is access-controlled for restricted users (who have accounts), and it's fundamentally not shared-cacheable, even if it has\nmax-age\n.\nYou can use the\npublic\ndirective to unlock that restriction.\nhttp\nCache-Control: public, max-age=604800\nNote that\ns-maxage\nor\nmust-revalidate\nalso unlock that restriction.\nIf a request doesn't have an\nAuthorization\nheader, or you are already using\ns-maxage\nor\nmust-revalidate\nin the response, then you don't need to use\npublic\n.\nmust-understand\nThe\nmust-understand\nresponse directive indicates that a cache should store the response only if it understands the requirements for caching based on status code.\nmust-understand\nshould be coupled with\nno-store\nfor fallback behavior.\nhttp\nCache-Control: must-understand, no-store\nIf a cache doesn't support\nmust-understand\n, it will be ignored. If\nno-store\nis also present, the response isn't stored.\nIf a cache supports\nmust-understand\n, it stores the response with an understanding of cache requirements based on its status code.\nno-transform\nSome intermediaries transform content for various reasons. For example, some convert images to reduce transfer size. In some cases, this is undesirable for the content provider.\nno-transform\nindicates that any intermediary (regardless of whether it implements a cache) shouldn't transform the response contents.\nimmutable\nThe\nimmutable\nresponse directive indicates that the response will not be updated while it's\nfresh\n.\nhttp\nCache-Control: public, max-age=604800, immutable\nA modern best practice for static resources is to include version\/hashes in their URLs, while never modifying the resources — but instead, when necessary,\nupdating\nthe resources with newer versions that have new version-numbers\/hashes, so that their URLs are different. That's called the\ncache-busting\npattern.\nhtml\n<script src=\"https:\/\/example.com\/react.0.0.0.js\"><\/script>\nWhen a user reloads the browser, the browser will send conditional requests for validating to the origin server. But it's not necessary to revalidate those kinds of static resources even when a user reloads the browser, because they're never modified.\nimmutable\ntells a cache that the response is immutable while it's\nfresh\nand avoids those kinds of unnecessary conditional requests to the server.\nWhen you use a cache-busting pattern for resources and apply them to a long\nmax-age\n, you can also add\nimmutable\nto avoid revalidation.\nstale-while-revalidate\nThe\nstale-while-revalidate\nresponse directive indicates that the cache could reuse a stale response while it revalidates it to a cache.\nhttp\nCache-Control: max-age=604800, stale-while-revalidate=86400\nIn the example above, the response is\nfresh\nfor 7 days (604800s).\nAfter 7 days it becomes\nstale\n, but the cache is allowed to reuse it for any requests that are made in the following day (86400s), provided that they revalidate the response in the background.\nRevalidation will make the cache be\nfresh\nagain, so it appears to clients that it was always\nfresh\nduring that period — effectively hiding the latency penalty of revalidation from them.\nIf no request happened during that period, the cache became\nstale\nand the next request will revalidate normally.\nstale-if-error\nThe\nstale-if-error\nresponse directive indicates that the cache can reuse a\nstale response\nwhen an upstream server generates an error, or when the error is generated locally. Here, an error is considered any response with a status code of 500, 502, 503, or 504.\nhttp\nCache-Control: max-age=604800, stale-if-error=86400\nIn the example above, the response is\nfresh\nfor 7 days (604800s). Afterwards, it becomes\nstale\n, but can be used for an extra 1 day (86400s) when an error is encountered.\nAfter the stale-if-error period passes, the client will receive any error generated.\nRequest Directives\nno-cache\nThe\nno-cache\nrequest directive asks caches to validate the response with the origin server before reuse.\nhttp\nCache-Control: no-cache\nno-cache\nallows clients to request the most up-to-date response even if the cache has a\nfresh\nresponse.\nBrowsers usually add\nno-cache\nto requests when users are\nforce reloading\na page.\nno-store\nThe\nno-store\nrequest directive allows a client to request that caches refrain from storing the request and corresponding response — even if the origin server's response could be stored.\nhttp\nCache-Control: no-store\nmax-age\nThe\nmax-age=N\nrequest directive indicates that the client allows a stored response that is generated on the origin server within\nN\nseconds — where\nN\nmay be any non-negative integer (including\n0\n).\nhttp\nCache-Control: max-age=10800\nIn the case above, if the response with\nCache-Control: max-age=10800\nwas generated more than 3 hours ago (calculated from\nmax-age\nand the\nAge\nheader), the cache couldn't reuse that response.\nMany browsers use this directive for\nreloading\n, as explained below.\nhttp\nCache-Control: max-age=0\nmax-age=0\nis a workaround for\nno-cache\n, because many old (HTTP\/1.0) cache implementations don't support\nno-cache\n. Recently browsers are still using\nmax-age=0\nin \"reloading\" — for backward compatibility — and alternatively using\nno-cache\nto cause a \"force reloading\".\nIf the\nmax-age\nvalue is negative (for example,\n-1\n) or isn't an integer (for example,\n3599.99\n), then the caching behavior is unspecified. Caches are encouraged to treat the value as if it were\n0\n.\nmax-stale\nThe\nmax-stale=N\nrequest directive indicates that the client allows a stored response that is\nstale\nwithin\nN\nseconds.\nIf no\nN\nvalue is specified, the client will accept a stale response of any age.\nhttp\nCache-Control: max-stale=3600\nFor example, a request with the header above indicates that the browser will accept a stale response from the cache that has expired within the last hour.\nClients can use this header when the origin server is down or too slow and can accept cached responses from caches even if they are a bit old.\nNote that the major browsers do not support requests with\nmax-stale\n.\nmin-fresh\nThe\nmin-fresh=N\nrequest directive indicates that the client allows a stored response that is\nfresh\nfor at least\nN\nseconds.\nhttp\nCache-Control: min-fresh=600\nIn the case above, if the response with\nCache-Control: max-age=3600\nwas stored in caches 51 minutes ago, the cache couldn't reuse that response.\nClients can use this header when the user requires the response to not only be\nfresh\n, but also requires that it won't be updated for a period of time.\nNote that the major browsers do not support requests with\nmin-fresh\n.\nno-transform\nSame meaning that\nno-transform\nhas for a response, but for a request instead.\nonly-if-cached\nThe client indicates that an already-cached response should be returned. If a cache has a stored response, even a stale one, it will be returned. If no cached response is available, a\n504 Gateway Timeout\nresponse will be returned.\nstale-if-error\nThe\nstale-if-error\nrequest directive indicates that the browser is interested in receiving stale content on error from any intermediate server for a particular origin.\nThis is not supported by any browser (see\nBrowser compatibility\n).\nUse Cases\nPreventing storing\nIf you don't want a response stored in caches, use the\nno-store\ndirective.\nhttp\nCache-Control: no-store\nNote that\nno-cache\nmeans \"it can be stored but don't reuse before validating\" — so it's not for preventing a response from being stored.\nhttp\nCache-Control: no-cache\nIn theory, if directives are conflicted, the most restrictive directive should be honored. So the example below is basically meaningless because\nprivate\n,\nno-cache\n,\nmax-age=0\nand\nmust-revalidate\nconflict with\nno-store\n.\nhttp\n# conflicted\nCache-Control: private, no-cache, no-store, max-age=0, must-revalidate\n\n# equivalent to\nCache-Control: no-store\nCaching static assets with \"cache busting\"\nWhen you build static assets with versioning\/hashing mechanisms, adding a version\/hash to the filename or query string is a good way to manage caching.\nFor example:\nhtml\n\n<script src=\"\/assets\/react.min.js\"><\/script>\n<img src=\"\/assets\/hero.png\" width=\"900\" height=\"400\" \/>\nThe React library version will change when you update the library, and\nhero.png\nwill also change when you edit the picture. So those are hard to store in a cache with\nmax-age\n.\nIn such a case, you could address the caching needs by using a specific, numbered version of the library, and including the hash of the picture in its URL.\nhtml\n\n<script src=\"\/assets\/react.0.0.0min.js\"><\/script>\n<img src=\"\/assets\/hero.png?hash=deadbeef\" width=\"900\" height=\"400\" \/>\nYou can add a long\nmax-age\nvalue and\nimmutable\nbecause the content will never change.\nhttp\n# \/assets\/*\nCache-Control: max-age=31536000, immutable\nWhen you update the library or edit the picture, new content should have a new URL, and caches aren't reused. That is called the \"cache busting\" pattern.\nUse a\nno-cache\nto make sure that the HTML response itself is not cached.\nno-cache\ncould cause revalidation, and the client will correctly receive a new version of the HTML response and static assets.\nhttp\n# \/index.html\nCache-Control: no-cache\nNote: If\nindex.html\nis controlled under Basic Authentication or Digest Authentication, files under\n\/assets\nare not stored in the shared cache. If\n\/assets\/\nfiles are suitable for storing in a shared cache, you also need one of\npublic\n,\ns-maxage\nor\nmust-revalidate\n.\nUp-to-date contents always\nFor content that's generated dynamically, or that's static but updated often, you want a user to always receive the most up-to-date version.\nIf you don't add a\nCache-Control\nheader because the response is not intended to be cached, that could cause an unexpected result. Cache storage is allowed to cache it heuristically — so if you have any requirements on caching, you should always indicate them explicitly, in the\nCache-Control\nheader.\nAdding\nno-cache\nto the response causes revalidation to the server, so you can serve a\nfresh\nresponse every time — or if the client already has a new one, just respond\n304 Not Modified\n.\nhttp\nCache-Control: no-cache\nMost HTTP\/1.0 caches don't support\nno-cache\ndirectives, so historically\nmax-age=0\nwas used as a workaround. But only\nmax-age=0\ncould cause a\nstale response\nto be reused when caches disconnected from the origin server.\nmust-revalidate\naddresses that. That's why the example below is equivalent to\nno-cache\n.\nhttp\nCache-Control: max-age=0, must-revalidate\nBut for now, you can simply use\nno-cache\ninstead.\nClearing an already-stored cache\nThere are no cache directives for clearing already-stored responses from caches on\nintermediate\nservers.\nImagine that clients\/caches store a\nfresh\nresponse for a path, with no request flight to the server. There is nothing a server could do to that path.\nClear-Site-Data: cache\ncan be used to clear every stored response for a site in the browser cache, so use this with care.\nNote that this will not affect shared or intermediate caches.\nSpecifications\nSpecification\nHTTP Caching\n# field.cache-control\nHTTP Immutable Responses\n# the-immutable-cache-control-extension\nBrowser compatibility\nSee also\nHTTP caching\nCaching Tutorial for Web Authors and Webmasters\nCaching best practices & max-age gotchas\nCache-Control for Civilians\nRFC 9111 – HTTP Caching\nRFC 5861 – HTTP Cache-Control Extensions for Stale Content\nRFC 8246 – HTTP Immutable Responses","attrs_markdown":"- [Skip to main content](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#content)\n- [Skip to search](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#search)\n\nHTML\n\n[HTML: Markup 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[Web](https:\/\/developer.mozilla.org\/en-US\/docs\/Web)\n2. [HTTP](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP)\n3. [Reference](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference)\n4. [Headers](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers)\n5. [Cache-Control](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control)\n\n# Cache-Control header\nBaseline  Widely available\n\nThis feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.\n\n- [Learn more](https:\/\/developer.mozilla.org\/en-US\/docs\/Glossary\/Baseline\/Compatibility)\n- [See full compatibility](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#browser_compatibility)\n- [Report feedback](https:\/\/survey.alchemer.com\/s3\/7634825\/MDN-baseline-feedback?page=%2Fen-US%2Fdocs%2FWeb%2FHTTP%2FReference%2FHeaders%2FCache-Control&level=high)\n\nThe HTTP **`Cache-Control`** header holds *directives* (instructions) in both requests and responses that control [caching](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching) in browsers and shared caches (e.g., Proxies, CDNs).\n\n|   |   |\n|---|---|\n| Header type | [Request header](https:\/\/developer.mozilla.org\/en-US\/docs\/Glossary\/Request_header), [Response header](https:\/\/developer.mozilla.org\/en-US\/docs\/Glossary\/Response_header) |\n| [Forbidden request header](https:\/\/developer.mozilla.org\/en-US\/docs\/Glossary\/Forbidden_request_header) | No |\n| [CORS-safelisted response header](https:\/\/developer.mozilla.org\/en-US\/docs\/Glossary\/CORS-safelisted_response_header) | Yes |\n\n## In this article\n- [Syntax](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#syntax)\n- [Vocabulary](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#vocabulary)\n- [Directives](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#directives)\n- [Use Cases](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#use_cases)\n- [Specifications](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#specifications)\n- [Browser compatibility](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#browser_compatibility)\n- [See also](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#see_also)\n\n## [Syntax](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#syntax)\nhttp\n```\nCache-Control: <directive>, <directive>, ...\n```\n\nCache directives follow these rules:\n\n- Caching directives are case-insensitive. However, lowercase is recommended because some implementations do not recognize uppercase directives.\n- Multiple directives are permitted and must be comma-separated (e.g., `Cache-control: max-age=180, public`).\n- Some directives have an optional argument. When an argument is provided, it is separated from the directive name by an equals symbol (`=`). Typically, arguments for the directives are integers and are therefore not enclosed in quote characters (e.g., `Cache-control: max-age=12`).\n\n### [Cache directives](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#cache_directives)\nThe following table lists the standard `Cache-Control` directives:\n\n| Request | Response |\n|---|---|\n| `max-age` | `max-age` |\n| `max-stale` | \\- |\n| `min-fresh` | \\- |\n| \\- | `s-maxage` |\n| `no-cache` | `no-cache` |\n| `no-store` | `no-store` |\n| `no-transform` | `no-transform` |\n| `only-if-cached` | \\- |\n| \\- | `must-revalidate` |\n| \\- | `proxy-revalidate` |\n| \\- | `must-understand` |\n| \\- | `private` |\n| \\- | `public` |\n| \\- | `immutable` |\n| \\- | `stale-while-revalidate` |\n| `stale-if-error` | `stale-if-error` |\n\nNote: Check the [compatibility table](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#browser_compatibility) for their support; user agents that don't recognize them should ignore them.\n\n## [Vocabulary](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#vocabulary)\nThis section defines the terms used in this document, some of which are from the specification.\n\n[(HTTP) cache](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#http_cache)\n\nImplementation that holds requests and responses for reusing in subsequent requests. It can be either a shared cache or a private cache.\n\n[Shared cache](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#shared_cache)\n\nCache that exists between the origin server and clients (e.g., Proxy, CDN). It stores a single response and reuses it with multiple users — so developers should avoid storing personalized contents to be cached in the shared cache.\n\n[Private cache](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#private_cache)\n\nCache that exists in the client. It is also called *local cache* or *browser cache*. It can store and reuse personalized content for a single user.\n\n[Store response](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#store_response)\n\nStore a response in caches when the response is cacheable. However, the cached response is not always reused as-is. (Usually, \"cache\" means storing a response.)\n\n[Reuse response](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#reuse_response)\n\nReuse cached responses for subsequent requests.\n\n[Revalidate response](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#revalidate_response)\n\nAsk the origin server whether or not the stored response is still [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age). Usually, the revalidation is done through a conditional request.\n\n[Fresh response](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#fresh_response)\n\nIndicates that the response is [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age). This usually means the response can be reused for subsequent requests, depending on request directives.\n\n[Stale response](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#stale_response)\n\nIndicates that the response is a [stale response](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age). This usually means the response can't be reused as-is. Cache storage isn't required to remove stale responses immediately because revalidation could change the response from being stale to being [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) again.\n\n[Age](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#age)\n\nThe time since a response was generated. It is a criterion for whether a response is [fresh or stale](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age).\n\n## [Directives](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#directives)\nThis section lists directives that affect caching — both response directives and request directives.\n\n### [Response Directives](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#response_directives)\n#### `max-age`\nThe `max-age=N` response directive indicates that the response remains [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) until *N* seconds after the response is generated.\n\nhttp\n```\nCache-Control: max-age=604800\n```\n\nIndicates that caches can store this response and reuse it for subsequent requests while it's [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age).\n\nNote that `max-age` is not the elapsed time since the response was received; it is the elapsed time since the response was generated on the origin server. So if the other cache(s) — on the network route taken by the response — store the response for 100 seconds (indicated using the `Age` response header field), the browser cache would deduct 100 seconds from its [freshness lifetime](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age).\n\nIf the `max-age` value is negative (for example, `-1`) or isn't an integer (for example, `3599.99`), then the caching behavior is unspecified. Caches are encouraged to treat the value as if it were `0` (this is noted in the [Calculating Freshness Lifetime](https:\/\/httpwg.org\/specs\/rfc9111.html#calculating.freshness.lifetime) section of the HTTP specification).\n\nhttp\n```\nCache-Control: max-age=604800\nAge: 100\n```\n#### `s-maxage`\nThe `s-maxage` response directive indicates how long the response remains [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) in a shared cache. The `s-maxage` directive is ignored by private caches, and overrides the value specified by the `max-age` directive or the `Expires` header for shared caches, if they are present.\n\nhttp\n```\nCache-Control: s-maxage=604800\n```\n#### `no-cache`\nThe `no-cache` response directive indicates that the response can be stored in caches, but the response must be validated with the origin server before each reuse, even when the cache is disconnected from the origin server.\n\nhttp\n```\nCache-Control: no-cache\n```\n\nIf you want caches to always check for content updates while reusing stored content, `no-cache` is the directive to use. It does this by requiring caches to revalidate each request with the origin server.\n\nNote that `no-cache` does not mean \"don't cache\". `no-cache` allows caches to store a response but requires them to revalidate it before reuse. If the sense of \"don't cache\" that you want is actually \"don't store\", then `no-store` is the directive to use.\n\n#### `must-revalidate`\nThe `must-revalidate` response directive indicates that the response can be stored in caches and can be reused while [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age). If the response becomes [stale](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age), it must be validated with the origin server before reuse.\n\nTypically, `must-revalidate` is used with `max-age`.\n\nhttp\n```\nCache-Control: max-age=604800, must-revalidate\n```\n\nHTTP allows caches to reuse [stale responses](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) when they are disconnected from the origin server. `must-revalidate` is a way to prevent this from happening - either the stored response is revalidated with the origin server or a 504 (Gateway Timeout) response is generated.\n\n#### `proxy-revalidate`\nThe `proxy-revalidate` response directive is the equivalent of `must-revalidate`, but specifically for shared caches only.\n\n#### `no-store`\nThe `no-store` response directive indicates that any caches of any kind (private or shared) should not store this response.\n\nhttp\n```\nCache-Control: no-store\n```\n#### `private`\nThe `private` response directive indicates that the response can be stored only in a private cache (e.g., local caches in browsers).\n\nhttp\n```\nCache-Control: private\n```\n\nYou should add the `private` directive for user-personalized content, especially for responses received after login and for sessions managed via cookies.\n\nIf you forget to add `private` to a response with personalized content, then that response can be stored in a shared cache and end up being reused for multiple users, which can cause personal information to leak.\n\n#### `public`\nThe `public` response directive indicates that the response can be stored in a shared cache. Responses for requests with `Authorization` header fields must not be stored in a shared cache; however, the `public` directive will cause such responses to be stored in a shared cache.\n\nhttp\n```\nCache-Control: public\n```\n\nIn general, when pages are under Basic Auth or Digest Auth, the browser sends requests with the `Authorization` header. This means that the response is access-controlled for restricted users (who have accounts), and it's fundamentally not shared-cacheable, even if it has `max-age`.\n\nYou can use the `public` directive to unlock that restriction.\n\nhttp\n```\nCache-Control: public, max-age=604800\n```\n\nNote that `s-maxage` or `must-revalidate` also unlock that restriction.\n\nIf a request doesn't have an `Authorization` header, or you are already using `s-maxage` or `must-revalidate` in the response, then you don't need to use `public`.\n\n#### `must-understand`\nThe `must-understand` response directive indicates that a cache should store the response only if it understands the requirements for caching based on status code.\n\n`must-understand` should be coupled with `no-store` for fallback behavior.\n\nhttp\n```\nCache-Control: must-understand, no-store\n```\n\nIf a cache doesn't support `must-understand`, it will be ignored. If `no-store` is also present, the response isn't stored.\n\nIf a cache supports `must-understand`, it stores the response with an understanding of cache requirements based on its status code.\n\n#### `no-transform`\nSome intermediaries transform content for various reasons. For example, some convert images to reduce transfer size. In some cases, this is undesirable for the content provider.\n\n`no-transform` indicates that any intermediary (regardless of whether it implements a cache) shouldn't transform the response contents.\n\n#### `immutable`\nThe `immutable` response directive indicates that the response will not be updated while it's [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age).\n\nhttp\n```\nCache-Control: public, max-age=604800, immutable\n```\n\nA modern best practice for static resources is to include version\/hashes in their URLs, while never modifying the resources — but instead, when necessary, *updating* the resources with newer versions that have new version-numbers\/hashes, so that their URLs are different. That's called the **cache-busting** pattern.\n\nhtml\n```\n<script src=\"https:\/\/example.com\/react.0.0.0.js\"><\/script>\n```\n\nWhen a user reloads the browser, the browser will send conditional requests for validating to the origin server. But it's not necessary to revalidate those kinds of static resources even when a user reloads the browser, because they're never modified. `immutable` tells a cache that the response is immutable while it's [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) and avoids those kinds of unnecessary conditional requests to the server.\n\nWhen you use a cache-busting pattern for resources and apply them to a long `max-age`, you can also add `immutable` to avoid revalidation.\n\n#### `stale-while-revalidate`\nThe `stale-while-revalidate` response directive indicates that the cache could reuse a stale response while it revalidates it to a cache.\n\nhttp\n```\nCache-Control: max-age=604800, stale-while-revalidate=86400\n```\n\nIn the example above, the response is [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) for 7 days (604800s). After 7 days it becomes [stale](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age), but the cache is allowed to reuse it for any requests that are made in the following day (86400s), provided that they revalidate the response in the background.\n\nRevalidation will make the cache be [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) again, so it appears to clients that it was always [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) during that period — effectively hiding the latency penalty of revalidation from them.\n\nIf no request happened during that period, the cache became [stale](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) and the next request will revalidate normally.\n\n#### `stale-if-error`\nThe `stale-if-error` response directive indicates that the cache can reuse a [stale response](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) when an upstream server generates an error, or when the error is generated locally. Here, an error is considered any response with a status code of 500, 502, 503, or 504.\n\nhttp\n```\nCache-Control: max-age=604800, stale-if-error=86400\n```\n\nIn the example above, the response is [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) for 7 days (604800s). Afterwards, it becomes [stale](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age), but can be used for an extra 1 day (86400s) when an error is encountered.\n\nAfter the stale-if-error period passes, the client will receive any error generated.\n\n### [Request Directives](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#request_directives)\n#### `no-cache`\nThe `no-cache` request directive asks caches to validate the response with the origin server before reuse.\n\nhttp\n```\nCache-Control: no-cache\n```\n\n`no-cache` allows clients to request the most up-to-date response even if the cache has a [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) response.\n\nBrowsers usually add `no-cache` to requests when users are **force reloading** a page.\n\n#### `no-store`\nThe `no-store` request directive allows a client to request that caches refrain from storing the request and corresponding response — even if the origin server's response could be stored.\n\nhttp\n```\nCache-Control: no-store\n```\n#### `max-age`\nThe `max-age=N` request directive indicates that the client allows a stored response that is generated on the origin server within *N* seconds — where *N* may be any non-negative integer (including `0`).\n\nhttp\n```\nCache-Control: max-age=10800\n```\n\nIn the case above, if the response with `Cache-Control: max-age=10800` was generated more than 3 hours ago (calculated from `max-age` and the `Age` header), the cache couldn't reuse that response.\n\nMany browsers use this directive for **reloading**, as explained below.\n\nhttp\n```\nCache-Control: max-age=0\n```\n\n`max-age=0` is a workaround for `no-cache`, because many old (HTTP\/1.0) cache implementations don't support `no-cache`. Recently browsers are still using `max-age=0` in \"reloading\" — for backward compatibility — and alternatively using `no-cache` to cause a \"force reloading\".\n\nIf the `max-age` value is negative (for example, `-1`) or isn't an integer (for example, `3599.99`), then the caching behavior is unspecified. Caches are encouraged to treat the value as if it were `0`.\n\n#### `max-stale`\nThe `max-stale=N` request directive indicates that the client allows a stored response that is [stale](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) within *N* seconds. If no *N* value is specified, the client will accept a stale response of any age.\n\nhttp\n```\nCache-Control: max-stale=3600\n```\n\nFor example, a request with the header above indicates that the browser will accept a stale response from the cache that has expired within the last hour.\n\nClients can use this header when the origin server is down or too slow and can accept cached responses from caches even if they are a bit old.\n\nNote that the major browsers do not support requests with `max-stale`.\n\n#### `min-fresh`\nThe `min-fresh=N` request directive indicates that the client allows a stored response that is [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) for at least *N* seconds.\n\nhttp\n```\nCache-Control: min-fresh=600\n```\n\nIn the case above, if the response with `Cache-Control: max-age=3600` was stored in caches 51 minutes ago, the cache couldn't reuse that response.\n\nClients can use this header when the user requires the response to not only be [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age), but also requires that it won't be updated for a period of time.\n\nNote that the major browsers do not support requests with `min-fresh`.\n\n#### `no-transform`\nSame meaning that `no-transform` has for a response, but for a request instead.\n\n#### `only-if-cached`\nThe client indicates that an already-cached response should be returned. If a cache has a stored response, even a stale one, it will be returned. If no cached response is available, a [504 Gateway Timeout](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/504) response will be returned.\n\n#### `stale-if-error`\nThe `stale-if-error` request directive indicates that the browser is interested in receiving stale content on error from any intermediate server for a particular origin. This is not supported by any browser (see [Browser compatibility](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#browser_compatibility)).\n## [Use Cases](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#use_cases)\n### [Preventing storing](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#preventing_storing)\nIf you don't want a response stored in caches, use the `no-store` directive.\n\nhttp\n```\nCache-Control: no-store\n```\n\nNote that `no-cache` means \"it can be stored but don't reuse before validating\" — so it's not for preventing a response from being stored.\n\nhttp\n```\nCache-Control: no-cache\n```\n\nIn theory, if directives are conflicted, the most restrictive directive should be honored. So the example below is basically meaningless because `private`, `no-cache`, `max-age=0` and `must-revalidate` conflict with `no-store`.\n\nhttp\n```\n# conflicted\nCache-Control: private, no-cache, no-store, max-age=0, must-revalidate\n\n# equivalent to\nCache-Control: no-store\n```\n\n### [Caching static assets with \"cache busting\"](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#caching_static_assets_with_cache_busting)\nWhen you build static assets with versioning\/hashing mechanisms, adding a version\/hash to the filename or query string is a good way to manage caching.\n\nFor example:\n\nhtml\n```\n\n<script src=\"\/assets\/react.min.js\"><\/script>\n<img src=\"\/assets\/hero.png\" width=\"900\" height=\"400\" \/>\n```\n\nThe React library version will change when you update the library, and `hero.png` will also change when you edit the picture. So those are hard to store in a cache with `max-age`.\n\nIn such a case, you could address the caching needs by using a specific, numbered version of the library, and including the hash of the picture in its URL.\n\nhtml\n```\n\n<script src=\"\/assets\/react.0.0.0min.js\"><\/script>\n<img src=\"\/assets\/hero.png?hash=deadbeef\" width=\"900\" height=\"400\" \/>\n```\n\nYou can add a long `max-age` value and `immutable` because the content will never change.\n\nhttp\n```\n# \/assets\/*\nCache-Control: max-age=31536000, immutable\n```\n\nWhen you update the library or edit the picture, new content should have a new URL, and caches aren't reused. That is called the \"cache busting\" pattern.\n\nUse a `no-cache` to make sure that the HTML response itself is not cached. `no-cache` could cause revalidation, and the client will correctly receive a new version of the HTML response and static assets.\n\nhttp\n```\n# \/index.html\nCache-Control: no-cache\n```\n\nNote: If `index.html` is controlled under Basic Authentication or Digest Authentication, files under `\/assets` are not stored in the shared cache. If `\/assets\/` files are suitable for storing in a shared cache, you also need one of `public`, `s-maxage` or `must-revalidate`.\n\n### [Up-to-date contents always](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#up-to-date_contents_always)\nFor content that's generated dynamically, or that's static but updated often, you want a user to always receive the most up-to-date version.\n\nIf you don't add a `Cache-Control` header because the response is not intended to be cached, that could cause an unexpected result. Cache storage is allowed to cache it heuristically — so if you have any requirements on caching, you should always indicate them explicitly, in the `Cache-Control` header.\n\nAdding `no-cache` to the response causes revalidation to the server, so you can serve a [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) response every time — or if the client already has a new one, just respond `304 Not Modified`.\n\nhttp\n```\nCache-Control: no-cache\n```\n\nMost HTTP\/1.0 caches don't support `no-cache` directives, so historically `max-age=0` was used as a workaround. But only `max-age=0` could cause a [stale response](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) to be reused when caches disconnected from the origin server. `must-revalidate` addresses that. That's why the example below is equivalent to `no-cache`.\n\nhttp\n```\nCache-Control: max-age=0, must-revalidate\n```\n\nBut for now, you can simply use `no-cache` instead.\n\n### [Clearing an already-stored cache](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#clearing_an_already-stored_cache)\nThere are no cache directives for clearing already-stored responses from caches on *intermediate* servers.\n\nImagine that clients\/caches store a [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) response for a path, with no request flight to the server. There is nothing a server could do to that path.\n\n[`Clear-Site-Data: cache`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Clear-Site-Data#cache) can be used to clear every stored response for a site in the browser cache, so use this with care. Note that this will not affect shared or intermediate caches.\n\n## [Specifications](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#specifications)\n| Specification |\n|---|\n| [HTTP Caching \\# field.cache-control](https:\/\/httpwg.org\/specs\/rfc9111.html#field.cache-control) |\n| [HTTP Immutable Responses \\# the-immutable-cache-control-extension](https:\/\/httpwg.org\/specs\/rfc8246.html#the-immutable-cache-control-extension) |\n## [Browser compatibility](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#browser_compatibility)\n## [See also](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#see_also)\n- [HTTP caching](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching)\n- [Caching Tutorial for Web Authors and Webmasters](https:\/\/www.mnot.net\/cache_docs\/)\n- [Caching best practices & max-age gotchas](https:\/\/jakearchibald.com\/2016\/caching-best-practices\/)\n- [Cache-Control for Civilians](https:\/\/csswizardry.com\/2019\/03\/cache-control-for-civilians\/)\n- [RFC 9111 – HTTP Caching](https:\/\/httpwg.org\/specs\/rfc9111.html)\n- [RFC 5861 – HTTP Cache-Control Extensions for Stale Content](https:\/\/httpwg.org\/specs\/rfc5861.html)\n- [RFC 8246 – HTTP Immutable Responses](https:\/\/httpwg.org\/specs\/rfc8246.html)\n\n## Help improve MDN\n[Learn how to contribute](https:\/\/developer.mozilla.org\/en-US\/docs\/MDN\/Community\/Getting_started)\n\nThis page was last modified on Nov 16, 2025 by [MDN contributors](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control\/contributors.txt).\n\n[View this page on GitHub](https:\/\/github.com\/mdn\/content\/blob\/main\/files\/en-us\/web\/http\/reference\/headers\/cache-control\/index.md?plain=1 \"Folder: en-us\/web\/http\/reference\/headers\/cache-control (Opens in a new tab)\") • [Report a problem with this content](https:\/\/github.com\/mdn\/content\/issues\/new?template=page-report.yml&mdn-url=https%3A%2F%2Fdeveloper.mozilla.org%2Fen-US%2Fdocs%2FWeb%2FHTTP%2FReference%2FHeaders%2FCache-Control&metadata=%3C%21--+Do+not+make+changes+below+this+line+--%3E%0A%3Cdetails%3E%0A%3Csummary%3EPage+report+details%3C%2Fsummary%3E%0A%0A*+Folder%3A+%60en-us%2Fweb%2Fhttp%2Freference%2Fheaders%2Fcache-control%60%0A*+MDN+URL%3A+https%3A%2F%2Fdeveloper.mozilla.org%2Fen-US%2Fdocs%2FWeb%2FHTTP%2FReference%2FHeaders%2FCache-Control%0A*+GitHub+URL%3A+https%3A%2F%2Fgithub.com%2Fmdn%2Fcontent%2Fblob%2Fmain%2Ffiles%2Fen-us%2Fweb%2Fhttp%2Freference%2Fheaders%2Fcache-control%2Findex.md%0A*+Last+commit%3A+https%3A%2F%2Fgithub.com%2Fmdn%2Fcontent%2Fcommit%2Ffd4cf672d03417a8a391a74db10dfda3cb1e8443%0A*+Document+last+modified%3A+2025-11-16T23%3A18%3A00.000Z%0A%0A%3C%2Fdetails%3E \"This will take you to GitHub to file a new issue.\")\n\n1. [HTTP](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP)\n2. [Guides](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides)\n3. [Overview of HTTP](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Overview)\n4. [Evolution of HTTP](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Evolution_of_HTTP)\n5. [A typical HTTP session](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Session)\n6. [HTTP messages](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Messages)\n7. [Media types](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/MIME_types)\n   1. [Common types](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/MIME_types\/Common_types)\n8. [Compression in HTTP](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Compression)\n9. [HTTP caching](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching)\n10. [HTTP authentication](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Authentication)\n11. [Using HTTP cookies](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Cookies)\n12. [Redirections in HTTP](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Redirections)\n13. [Conditional requests](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Conditional_requests)\n14. [Range requests](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Range_requests)\n15. [Client hints](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Client_hints)\n16. [User-Agent reduction](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/User-agent_reduction)\n17. [Compression Dictionary Transport](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Compression_dictionary_transport)\n    Experimental\n18. [Network Error Logging](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Network_Error_Logging)\n    Experimental\n19. [Content negotiation](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Content_negotiation)\n    1. [Default Accept values](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Content_negotiation\/List_of_default_Accept_values)\n20. [Browser detection using the UA string](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Browser_detection_using_the_user_agent)\n21. [Connection management in HTTP\/1.x](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Connection_management_in_HTTP_1.x)\n22. [Protocol upgrade mechanism](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Protocol_upgrade_mechanism)\n23. [Proxy servers and tunneling](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Proxy_servers_and_tunneling)\n    1. [Proxy Auto-Configuration (PAC) file](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Proxy_servers_and_tunneling\/Proxy_Auto-Configuration_PAC_file)\n24. Security and privacy\n    \n    1. [HTTP Observatory](https:\/\/developer.mozilla.org\/en-US\/observatory)\n    2. [Practical implementation guides](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/Security\/Practical_implementation_guides)\n    3. [Permissions Policy](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Permissions_Policy)\n       Experimental\n    4. [Cross-Origin Resource Policy (CORP)](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Cross-Origin_Resource_Policy)\n    5. [IFrame credentialless](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/IFrame_credentialless)\n       Experimental\n    6. [Fetch metadata](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Fetch_metadata)\n    7. [Cross-Origin Resource Sharing (CORS)](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/CORS)\n    8. [CORS errors](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/CORS\/Errors)\n       \n       1. [`Reason: CORS disabled`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/CORS\/Errors\/CORSDisabled)\n       2. [`Reason: CORS header 'Access-Control-Allow-Origin' does not match 'xyz'`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/CORS\/Errors\/CORSAllowOriginNotMatchingOrigin)\n       3. [`Reason: CORS header 'Access-Control-Allow-Origin' missing`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/CORS\/Errors\/CORSMissingAllowOrigin)\n       4. [`Reason: CORS header 'Origin' cannot be added`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/CORS\/Errors\/CORSOriginHeaderNotAdded)\n       5. [`Reason: CORS preflight channel did not succeed`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/CORS\/Errors\/CORSPreflightDidNotSucceed)\n       6. [`Reason: CORS request did not succeed`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/CORS\/Errors\/CORSDidNotSucceed)\n       7. [`Reason: CORS request external redirect not allowed`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/CORS\/Errors\/CORSExternalRedirectNotAllowed)\n       8. [`Reason: CORS request not HTTP`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/CORS\/Errors\/CORSRequestNotHttp)\n       9. [`Reason: Credential is not supported if the CORS header 'Access-Control-Allow-Origin' is '*'`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/CORS\/Errors\/CORSNotSupportingCredentials)\n       10. [`Reason: Did not find method in CORS header 'Access-Control-Allow-Methods'`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/CORS\/Errors\/CORSMethodNotFound)\n       11. [`Reason: expected 'true' in CORS header 'Access-Control-Allow-Credentials'`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/CORS\/Errors\/CORSMIssingAllowCredentials)\n       12. [`Reason: invalid token 'xyz' in CORS header 'Access-Control-Allow-Headers'`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/CORS\/Errors\/CORSInvalidAllowHeader)\n       13. [`Reason: invalid token 'xyz' in CORS header 'Access-Control-Allow-Methods'`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/CORS\/Errors\/CORSInvalidAllowMethod)\n       14. [`Reason: missing token 'xyz' in CORS header 'Access-Control-Allow-Headers' from CORS preflight channel`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/CORS\/Errors\/CORSMissingAllowHeaderFromPreflight)\n       15. [`Reason: Multiple CORS header 'Access-Control-Allow-Origin' not allowed`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/CORS\/Errors\/CORSMultipleAllowOriginNotAllowed)\n    9. [Content Security Policy (CSP)](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/CSP)\n       \n       1. [Errors and warnings](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/CSP\/Errors)\n25. [Reference](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference)\n26. [HTTP headers](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers)\n    \n    1. [`Accept`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Accept)\n    2. [`Accept-CH`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Accept-CH)\n    3. [`Accept-Encoding`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Accept-Encoding)\n    4. [`Accept-Language`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Accept-Language)\n    5. [`Accept-Patch`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Accept-Patch)\n    6. [`Accept-Post`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Accept-Post)\n    7. [`Accept-Ranges`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Accept-Ranges)\n    8. [`Access-Control-Allow-Credentials`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Access-Control-Allow-Credentials)\n    9. [`Access-Control-Allow-Headers`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Access-Control-Allow-Headers)\n    10. [`Access-Control-Allow-Methods`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Access-Control-Allow-Methods)\n    11. [`Access-Control-Allow-Origin`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Access-Control-Allow-Origin)\n    12. [`Access-Control-Expose-Headers`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Access-Control-Expose-Headers)\n    13. [`Access-Control-Max-Age`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Access-Control-Max-Age)\n    14. [`Access-Control-Request-Headers`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Access-Control-Request-Headers)\n    15. [`Access-Control-Request-Method`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Access-Control-Request-Method)\n    16. [`Activate-Storage-Access`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Activate-Storage-Access)\n    17. [`Age`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Age)\n    18. [`Allow`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Allow)\n    19. [`Alt-Svc`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Alt-Svc)\n    20. [`Alt-Used`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Alt-Used)\n    21. [`Attribution-Reporting-Eligible`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Attribution-Reporting-Eligible)\n        Deprecated\n    22. [`Attribution-Reporting-Register-Source`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Attribution-Reporting-Register-Source)\n        Deprecated\n    23. [`Attribution-Reporting-Register-Trigger`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Attribution-Reporting-Register-Trigger)\n        Deprecated\n    24. [`Authorization`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Authorization)\n    25. [`Available-Dictionary`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Available-Dictionary)\n        Experimental\n    26. *[`Cache-Control`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control)*\n    27. [`Clear-Site-Data`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Clear-Site-Data)\n    28. [`Connection`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Connection)\n    29. [`Content-Digest`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Digest)\n    30. [`Content-Disposition`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Disposition)\n    31. [`Content-DPR`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-DPR)\n        Non-standard\n        Deprecated\n    32. [`Content-Encoding`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Encoding)\n    33. [`Content-Language`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Language)\n    34. [`Content-Length`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Length)\n    35. [`Content-Location`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Location)\n    36. [`Content-Range`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Range)\n    37. [`Content-Security-Policy`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy)\n    38. [`Content-Security-Policy-Report-Only`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy-Report-Only)\n    39. [`Content-Type`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Type)\n    40. [`Cookie`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cookie)\n    41. [`Critical-CH`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Critical-CH)\n        Experimental\n    42. [`Cross-Origin-Embedder-Policy`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cross-Origin-Embedder-Policy)\n    43. [`Cross-Origin-Embedder-Policy-Report-Only`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cross-Origin-Embedder-Policy-Report-Only)\n    44. [`Cross-Origin-Opener-Policy`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cross-Origin-Opener-Policy)\n    45. [`Cross-Origin-Resource-Policy`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cross-Origin-Resource-Policy)\n    46. [`Date`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Date)\n    47. [`Device-Memory`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Device-Memory)\n        Non-standard\n        Deprecated\n    48. [`Dictionary-ID`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Dictionary-ID)\n        Experimental\n    49. [`DNT`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/DNT)\n        Non-standard\n        Deprecated\n    50. [`Downlink`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Downlink)\n        Experimental\n    51. [`DPR`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/DPR)\n        Non-standard\n        Deprecated\n    52. [`Early-Data`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Early-Data)\n        Experimental\n    53. [`ECT`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/ECT)\n        Experimental\n    54. [`ETag`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/ETag)\n    55. [`Expect`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Expect)\n    56. [`Expect-CT`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Expect-CT)\n        Deprecated\n    57. [`Expires`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Expires)\n    58. [`Forwarded`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Forwarded)\n    59. [`From`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/From)\n    60. [`Host`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Host)\n    61. [`Idempotency-Key`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Idempotency-Key)\n        Experimental\n    62. [`If-Match`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/If-Match)\n    63. [`If-Modified-Since`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/If-Modified-Since)\n    64. [`If-None-Match`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/If-None-Match)\n    65. [`If-Range`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/If-Range)\n    66. [`If-Unmodified-Since`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/If-Unmodified-Since)\n    67. [`Integrity-Policy`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Integrity-Policy)\n    68. [`Integrity-Policy-Report-Only`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Integrity-Policy-Report-Only)\n    69. [`Keep-Alive`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Keep-Alive)\n    70. [`Last-Modified`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Last-Modified)\n    71. [`Link`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Link)\n    72. [`Location`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Location)\n    73. [`Max-Forwards`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Max-Forwards)\n    74. [`NEL`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/NEL)\n        Experimental\n    75. [`No-Vary-Search`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/No-Vary-Search)\n        Experimental\n    76. [`Observe-Browsing-Topics`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Observe-Browsing-Topics)\n        Non-standard\n        Deprecated\n    77. [`Origin`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Origin)\n    78. [`Origin-Agent-Cluster`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Origin-Agent-Cluster)\n    79. [`Permissions-Policy`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy)\n        Experimental\n    80. [`Pragma`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Pragma)\n        Deprecated\n    81. [`Prefer`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Prefer)\n    82. [`Preference-Applied`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Preference-Applied)\n    83. [`Priority`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Priority)\n    84. [`Proxy-Authenticate`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Proxy-Authenticate)\n    85. [`Proxy-Authorization`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Proxy-Authorization)\n    86. [`Range`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Range)\n    87. [`Referer`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Referer)\n    88. [`Referrer-Policy`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Referrer-Policy)\n    89. [`Refresh`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Refresh)\n    90. [`Report-To`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Report-To)\n        Non-standard\n        Deprecated\n    91. [`Reporting-Endpoints`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Reporting-Endpoints)\n    92. [`Repr-Digest`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Repr-Digest)\n    93. [`Retry-After`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Retry-After)\n    94. [`RTT`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/RTT)\n        Experimental\n    95. [`Save-Data`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Save-Data)\n        Experimental\n    96. [`Sec-Browsing-Topics`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-Browsing-Topics)\n        Non-standard\n        Deprecated\n    97. [`Sec-CH-Device-Memory`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-CH-Device-Memory)\n        Experimental\n    98. [`Sec-CH-DPR`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-CH-DPR)\n        Experimental\n    99. [`Sec-CH-Prefers-Color-Scheme`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-CH-Prefers-Color-Scheme)\n        Experimental\n    100. [`Sec-CH-Prefers-Reduced-Motion`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-CH-Prefers-Reduced-Motion)\n         Experimental\n    101. [`Sec-CH-Prefers-Reduced-Transparency`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-CH-Prefers-Reduced-Transparency)\n         Experimental\n    102. [`Sec-CH-UA`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-CH-UA)\n         Experimental\n    103. [`Sec-CH-UA-Arch`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-CH-UA-Arch)\n         Experimental\n    104. [`Sec-CH-UA-Bitness`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-CH-UA-Bitness)\n         Experimental\n    105. [`Sec-CH-UA-Form-Factors`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-CH-UA-Form-Factors)\n         Experimental\n    106. [`Sec-CH-UA-Full-Version`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-CH-UA-Full-Version)\n         Deprecated\n    107. [`Sec-CH-UA-Full-Version-List`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-CH-UA-Full-Version-List)\n         Experimental\n    108. [`Sec-CH-UA-Mobile`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-CH-UA-Mobile)\n         Experimental\n    109. [`Sec-CH-UA-Model`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-CH-UA-Model)\n         Experimental\n    110. [`Sec-CH-UA-Platform`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-CH-UA-Platform)\n         Experimental\n    111. [`Sec-CH-UA-Platform-Version`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-CH-UA-Platform-Version)\n         Experimental\n    112. [`Sec-CH-UA-WoW64`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-CH-UA-WoW64)\n         Experimental\n    113. [`Sec-CH-Viewport-Height`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-CH-Viewport-Height)\n         Experimental\n    114. [`Sec-CH-Viewport-Width`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-CH-Viewport-Width)\n         Experimental\n    115. [`Sec-CH-Width`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-CH-Width)\n         Experimental\n    116. [`Sec-Fetch-Dest`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-Fetch-Dest)\n    117. [`Sec-Fetch-Mode`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-Fetch-Mode)\n    118. [`Sec-Fetch-Site`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-Fetch-Site)\n    119. [`Sec-Fetch-Storage-Access`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-Fetch-Storage-Access)\n    120. [`Sec-Fetch-User`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-Fetch-User)\n    121. [`Sec-GPC`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-GPC)\n         Experimental\n    122. [`Sec-Private-State-Token`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-Private-State-Token)\n         Experimental\n    123. [`Sec-Private-State-Token-Crypto-Version`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-Private-State-Token-Crypto-Version)\n         Experimental\n    124. [`Sec-Private-State-Token-Lifetime`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-Private-State-Token-Lifetime)\n         Experimental\n    125. [`Sec-Purpose`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-Purpose)\n    126. [`Sec-Redemption-Record`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-Redemption-Record)\n         Experimental\n    127. [`Sec-Speculation-Tags`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-Speculation-Tags)\n         Experimental\n    128. [`Sec-WebSocket-Accept`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-WebSocket-Accept)\n    129. [`Sec-WebSocket-Extensions`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-WebSocket-Extensions)\n    130. [`Sec-WebSocket-Key`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-WebSocket-Key)\n    131. [`Sec-WebSocket-Protocol`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-WebSocket-Protocol)\n    132. [`Sec-WebSocket-Version`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Sec-WebSocket-Version)\n    133. [`Server`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Server)\n    134. [`Server-Timing`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Server-Timing)\n    135. [`Service-Worker`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Service-Worker)\n    136. [`Service-Worker-Allowed`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Service-Worker-Allowed)\n    137. [`Service-Worker-Navigation-Preload`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Service-Worker-Navigation-Preload)\n    138. [`Set-Cookie`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Set-Cookie)\n    139. [`Set-Login`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Set-Login)\n    140. [`SourceMap`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/SourceMap)\n    141. [`Speculation-Rules`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Speculation-Rules)\n         Experimental\n    142. [`Strict-Transport-Security`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Strict-Transport-Security)\n    143. [`Supports-Loading-Mode`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Supports-Loading-Mode)\n         Experimental\n    144. [`TE`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/TE)\n    145. [`Timing-Allow-Origin`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Timing-Allow-Origin)\n    146. [`Tk`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Tk)\n         Non-standard\n         Deprecated\n    147. [`Trailer`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Trailer)\n    148. [`Transfer-Encoding`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Transfer-Encoding)\n    149. [`Upgrade`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Upgrade)\n    150. [`Upgrade-Insecure-Requests`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Upgrade-Insecure-Requests)\n    151. [`Use-As-Dictionary`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Use-As-Dictionary)\n         Experimental\n    152. [`User-Agent`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/User-Agent)\n    153. [`Vary`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Vary)\n    154. [`Via`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Via)\n    155. [`Viewport-Width`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Viewport-Width)\n         Non-standard\n         Deprecated\n    156. [`Want-Content-Digest`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Want-Content-Digest)\n    157. [`Want-Repr-Digest`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Want-Repr-Digest)\n    158. [`Warning`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Warning)\n         Deprecated\n    159. [`Width`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Width)\n         Non-standard\n         Deprecated\n    160. [`WWW-Authenticate`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/WWW-Authenticate)\n    161. [`X-Content-Type-Options`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/X-Content-Type-Options)\n    162. [`X-DNS-Prefetch-Control`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/X-DNS-Prefetch-Control)\n         Non-standard\n    163. [`X-Forwarded-For`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/X-Forwarded-For)\n         Non-standard\n    164. [`X-Forwarded-Host`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/X-Forwarded-Host)\n         Non-standard\n    165. [`X-Forwarded-Proto`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/X-Forwarded-Proto)\n         Non-standard\n    166. [`X-Frame-Options`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/X-Frame-Options)\n    167. [`X-Permitted-Cross-Domain-Policies`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/X-Permitted-Cross-Domain-Policies)\n         Non-standard\n    168. [`X-Powered-By`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/X-Powered-By)\n         Non-standard\n    169. [`X-Robots-Tag`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/X-Robots-Tag)\n         Non-standard\n    170. [`X-XSS-Protection`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/X-XSS-Protection)\n         Non-standard\n         Deprecated\n27. [HTTP request methods](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Methods)\n    \n    1. [`CONNECT`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Methods\/CONNECT)\n    2. [`DELETE`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Methods\/DELETE)\n    3. [`GET`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Methods\/GET)\n    4. [`HEAD`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Methods\/HEAD)\n    5. [`OPTIONS`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Methods\/OPTIONS)\n    6. [`PATCH`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Methods\/PATCH)\n    7. [`POST`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Methods\/POST)\n    8. [`PUT`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Methods\/PUT)\n    9. [`TRACE`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Methods\/TRACE)\n28. [HTTP response status codes](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status)\n    \n    1. [`100 Continue`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/100)\n    2. [`101 Switching Protocols`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/101)\n    3. [`102 Processing`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/102)\n    4. [`103 Early Hints`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/103)\n    5. [`200 OK`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/200)\n    6. [`201 Created`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/201)\n    7. [`202 Accepted`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/202)\n    8. [`203 Non-Authoritative Information`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/203)\n    9. [`204 No Content`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/204)\n    10. [`205 Reset Content`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/205)\n    11. [`206 Partial Content`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/206)\n    12. [`207 Multi-Status`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/207)\n    13. [`208 Already Reported`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/208)\n    14. [`226 IM Used`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/226)\n    15. [`300 Multiple Choices`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/300)\n    16. [`301 Moved Permanently`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/301)\n    17. [`302 Found`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/302)\n    18. [`303 See Other`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/303)\n    19. [`304 Not Modified`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/304)\n    20. [`307 Temporary Redirect`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/307)\n    21. [`308 Permanent Redirect`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/308)\n    22. [`400 Bad Request`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/400)\n    23. [`401 Unauthorized`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/401)\n    24. [`402 Payment Required`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/402)\n    25. [`403 Forbidden`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/403)\n    26. [`404 Not Found`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/404)\n    27. [`405 Method Not Allowed`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/405)\n    28. [`406 Not Acceptable`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/406)\n    29. [`407 Proxy Authentication Required`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/407)\n    30. [`408 Request Timeout`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/408)\n    31. [`409 Conflict`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/409)\n    32. [`410 Gone`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/410)\n    33. [`411 Length Required`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/411)\n    34. [`412 Precondition Failed`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/412)\n    35. [`413 Content Too Large`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/413)\n    36. [`414 URI Too Long`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/414)\n    37. [`415 Unsupported Media Type`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/415)\n    38. [`416 Range Not Satisfiable`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/416)\n    39. [`417 Expectation Failed`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/417)\n    40. [`418 I'm a teapot`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/418)\n    41. [`421 Misdirected Request`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/421)\n    42. [`422 Unprocessable Content`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/422)\n    43. [`423 Locked`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/423)\n    44. [`424 Failed Dependency`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/424)\n    45. [`425 Too Early`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/425)\n    46. [`426 Upgrade Required`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/426)\n    47. [`428 Precondition Required`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/428)\n    48. [`429 Too Many Requests`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/429)\n    49. [`431 Request Header Fields Too Large`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/431)\n    50. [`451 Unavailable For Legal Reasons`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/451)\n    51. [`500 Internal Server Error`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/500)\n    52. [`501 Not Implemented`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/501)\n    53. [`502 Bad Gateway`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/502)\n    54. [`503 Service Unavailable`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/503)\n    55. [`504 Gateway Timeout`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/504)\n    56. [`505 HTTP Version Not Supported`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/505)\n    57. [`506 Variant Also Negotiates`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/506)\n    58. [`507 Insufficient Storage`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/507)\n    59. [`508 Loop Detected`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/508)\n    60. [`510 Not Extended`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/510)\n    61. [`511 Network Authentication Required`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/511)\n29. [CSP directives](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy#directives)\n    \n    1. [`base-uri`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/base-uri)\n    2. [`block-all-mixed-content`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/block-all-mixed-content)\n       Deprecated\n    3. [`child-src`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/child-src)\n    4. [`connect-src`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/connect-src)\n    5. [`default-src`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/default-src)\n    6. [`fenced-frame-src`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/fenced-frame-src)\n       Experimental\n    7. [`font-src`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/font-src)\n    8. [`form-action`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/form-action)\n    9. [`frame-ancestors`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/frame-ancestors)\n    10. [`frame-src`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/frame-src)\n    11. [`img-src`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/img-src)\n    12. [`manifest-src`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/manifest-src)\n    13. [`media-src`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/media-src)\n    14. [`object-src`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/object-src)\n    15. [`prefetch-src`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/prefetch-src)\n        Non-standard\n        Deprecated\n    16. [`report-to`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/report-to)\n    17. [`report-uri`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/report-uri)\n        Deprecated\n    18. [`require-trusted-types-for`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/require-trusted-types-for)\n    19. [`sandbox`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/sandbox)\n    20. [`script-src`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/script-src)\n    21. [`script-src-attr`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/script-src-attr)\n    22. [`script-src-elem`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/script-src-elem)\n    23. [`style-src`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/style-src)\n    24. [`style-src-attr`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/style-src-attr)\n    25. [`style-src-elem`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/style-src-elem)\n    26. [`trusted-types`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/trusted-types)\n    27. [`upgrade-insecure-requests`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/upgrade-insecure-requests)\n    28. [`worker-src`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Content-Security-Policy\/worker-src)\n30. [Permissions-Policy directives](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy#directives)\n    \n    Experimental\n    \n    1. [`accelerometer`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/accelerometer)\n       Experimental\n    2. [`ambient-light-sensor`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/ambient-light-sensor)\n       Experimental\n    3. [`aria-notify`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/aria-notify)\n       Experimental\n    4. [`attribution-reporting`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/attribution-reporting)\n       Deprecated\n    5. [`autoplay`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/autoplay)\n       Experimental\n    6. [`bluetooth`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/bluetooth)\n       Experimental\n    7. [`browsing-topics`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/browsing-topics)\n       Non-standard\n       Deprecated\n    8. [`camera`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/camera)\n       Experimental\n    9. [`captured-surface-control`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/captured-surface-control)\n       Experimental\n    10. [`ch-ua-high-entropy-values`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/ch-ua-high-entropy-values)\n        Experimental\n    11. [`compute-pressure`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/compute-pressure)\n        Experimental\n    12. [`cross-origin-isolated`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/cross-origin-isolated)\n        Experimental\n    13. [`deferred-fetch`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/deferred-fetch)\n        Experimental\n    14. [`deferred-fetch-minimal`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/deferred-fetch-minimal)\n        Experimental\n    15. [`display-capture`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/display-capture)\n        Experimental\n    16. [`encrypted-media`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/encrypted-media)\n        Experimental\n    17. [`fullscreen`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/fullscreen)\n        Experimental\n    18. [`gamepad`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/gamepad)\n        Experimental\n    19. [`geolocation`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/geolocation)\n        Experimental\n    20. [`gyroscope`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/gyroscope)\n        Experimental\n    21. [`hid`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/hid)\n        Experimental\n    22. [`identity-credentials-get`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/identity-credentials-get)\n        Experimental\n    23. [`idle-detection`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/idle-detection)\n        Experimental\n    24. [`language-detector`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/language-detector)\n        Experimental\n    25. [`local-fonts`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/local-fonts)\n        Experimental\n    26. [`magnetometer`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/magnetometer)\n        Experimental\n    27. [`microphone`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/microphone)\n        Experimental\n    28. [`midi`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/midi)\n        Experimental\n    29. [`on-device-speech-recognition`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/on-device-speech-recognition)\n        Experimental\n    30. [`otp-credentials`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/otp-credentials)\n        Experimental\n    31. [`payment`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/payment)\n        Experimental\n    32. [`picture-in-picture`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/picture-in-picture)\n        Experimental\n    33. [`private-state-token-issuance`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/private-state-token-issuance)\n        Experimental\n    34. [`private-state-token-redemption`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/private-state-token-redemption)\n        Experimental\n    35. [`publickey-credentials-create`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/publickey-credentials-create)\n        Experimental\n    36. [`publickey-credentials-get`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/publickey-credentials-get)\n        Experimental\n    37. [`screen-wake-lock`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/screen-wake-lock)\n        Experimental\n    38. [`serial`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/serial)\n        Experimental\n    39. [`speaker-selection`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/speaker-selection)\n        Experimental\n    40. [`storage-access`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/storage-access)\n        Experimental\n    41. [`summarizer`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/summarizer)\n        Experimental\n    42. [`translator`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/translator)\n        Experimental\n    43. [`usb`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/usb)\n        Experimental\n    44. [`web-share`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/web-share)\n        Experimental\n    45. [`window-management`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/window-management)\n        Experimental\n    46. [`xr-spatial-tracking`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Permissions-Policy\/xr-spatial-tracking)\n        Experimental\n31. [HTTP resources and specifications](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Resources_and_specifications)\n\nYour blueprint for a better internet.\n\nMDN\n\n- [About](https:\/\/developer.mozilla.org\/en-US\/about)\n- [Blog](https:\/\/developer.mozilla.org\/en-US\/blog\/)\n- [Mozilla careers](https:\/\/www.mozilla.org\/en-US\/careers\/listings\/)\n- [Advertise with us](https:\/\/developer.mozilla.org\/en-US\/advertising)\n- [MDN Plus](https:\/\/developer.mozilla.org\/en-US\/plus)\n- [Product help](https:\/\/support.mozilla.org\/products\/mdn-plus)\n\nContribute\n\n- [MDN Community](https:\/\/developer.mozilla.org\/en-US\/community)\n- [Community resources](https:\/\/developer.mozilla.org\/en-US\/docs\/MDN\/Community)\n- [Writing guidelines](https:\/\/developer.mozilla.org\/en-US\/docs\/MDN\/Writing_guidelines)\n- [MDN Discord](https:\/\/developer.mozilla.org\/discord)\n- [MDN on GitHub](https:\/\/github.com\/mdn)\n\nDevelopers\n\n- [Web technologies](https:\/\/developer.mozilla.org\/en-US\/docs\/Web)\n- [Learn web development](https:\/\/developer.mozilla.org\/en-US\/docs\/Learn_web_development)\n- [Guides](https:\/\/developer.mozilla.org\/en-US\/docs\/MDN\/Guides)\n- [Tutorials](https:\/\/developer.mozilla.org\/en-US\/docs\/MDN\/Tutorials)\n- [Glossary](https:\/\/developer.mozilla.org\/en-US\/docs\/Glossary)\n- [Hacks blog](https:\/\/hacks.mozilla.org\/)\n\n- [Website Privacy Notice](https:\/\/www.mozilla.org\/privacy\/websites\/)\n- [Telemetry Settings](https:\/\/www.mozilla.org\/en-US\/privacy\/websites\/data-preferences\/)\n- [Legal](https:\/\/www.mozilla.org\/about\/legal\/terms\/mozilla)\n- [Community Participation Guidelines](https:\/\/www.mozilla.org\/about\/governance\/policies\/participation\/)\n\nVisit [Mozilla Corporation’s](https:\/\/www.mozilla.org\/) not-for-profit parent, the [Mozilla Foundation](https:\/\/foundation.mozilla.org\/).  \n Portions of this content are ©1998–2026 by individual mozilla.org contributors. Content available under [a Creative Commons license](https:\/\/developer.mozilla.org\/docs\/MDN\/Writing_guidelines\/Attrib_copyright_license).","attrs_readable_markdown":"## [Syntax](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#syntax)\nhttp\n```\nCache-Control: <directive>, <directive>, ...\n```\n\nCache directives follow these rules:\n\n- Caching directives are case-insensitive. However, lowercase is recommended because some implementations do not recognize uppercase directives.\n- Multiple directives are permitted and must be comma-separated (e.g., `Cache-control: max-age=180, public`).\n- Some directives have an optional argument. When an argument is provided, it is separated from the directive name by an equals symbol (`=`). Typically, arguments for the directives are integers and are therefore not enclosed in quote characters (e.g., `Cache-control: max-age=12`).\n\n### [Cache directives](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#cache_directives)\nThe following table lists the standard `Cache-Control` directives:\n\n| Request | Response |\n|---|---|\n| `max-age` | `max-age` |\n| `max-stale` | \\- |\n| `min-fresh` | \\- |\n| \\- | `s-maxage` |\n| `no-cache` | `no-cache` |\n| `no-store` | `no-store` |\n| `no-transform` | `no-transform` |\n| `only-if-cached` | \\- |\n| \\- | `must-revalidate` |\n| \\- | `proxy-revalidate` |\n| \\- | `must-understand` |\n| \\- | `private` |\n| \\- | `public` |\n| \\- | `immutable` |\n| \\- | `stale-while-revalidate` |\n| `stale-if-error` | `stale-if-error` |\n\nNote: Check the [compatibility table](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#browser_compatibility) for their support; user agents that don't recognize them should ignore them.\n\n## [Vocabulary](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#vocabulary)\nThis section defines the terms used in this document, some of which are from the specification.\n\n[(HTTP) cache](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#http_cache)\n\nImplementation that holds requests and responses for reusing in subsequent requests. It can be either a shared cache or a private cache.\n\n[Shared cache](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#shared_cache)\n\nCache that exists between the origin server and clients (e.g., Proxy, CDN). It stores a single response and reuses it with multiple users — so developers should avoid storing personalized contents to be cached in the shared cache.\n\n[Private cache](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#private_cache)\n\nCache that exists in the client. It is also called *local cache* or *browser cache*. It can store and reuse personalized content for a single user.\n\n[Store response](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#store_response)\n\nStore a response in caches when the response is cacheable. However, the cached response is not always reused as-is. (Usually, \"cache\" means storing a response.)\n\n[Reuse response](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#reuse_response)\n\nReuse cached responses for subsequent requests.\n\n[Revalidate response](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#revalidate_response)\n\nAsk the origin server whether or not the stored response is still [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age). Usually, the revalidation is done through a conditional request.\n\n[Fresh response](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#fresh_response)\n\nIndicates that the response is [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age). This usually means the response can be reused for subsequent requests, depending on request directives.\n\n[Stale response](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#stale_response)\n\nIndicates that the response is a [stale response](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age). This usually means the response can't be reused as-is. Cache storage isn't required to remove stale responses immediately because revalidation could change the response from being stale to being [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) again.\n\n[Age](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#age)\n\nThe time since a response was generated. It is a criterion for whether a response is [fresh or stale](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age).\n\n## [Directives](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#directives)\nThis section lists directives that affect caching — both response directives and request directives.\n\n### [Response Directives](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#response_directives)\n#### `max-age`\nThe `max-age=N` response directive indicates that the response remains [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) until *N* seconds after the response is generated.\n\nhttp\n```\nCache-Control: max-age=604800\n```\n\nIndicates that caches can store this response and reuse it for subsequent requests while it's [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age).\n\nNote that `max-age` is not the elapsed time since the response was received; it is the elapsed time since the response was generated on the origin server. So if the other cache(s) — on the network route taken by the response — store the response for 100 seconds (indicated using the `Age` response header field), the browser cache would deduct 100 seconds from its [freshness lifetime](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age).\n\nIf the `max-age` value is negative (for example, `-1`) or isn't an integer (for example, `3599.99`), then the caching behavior is unspecified. Caches are encouraged to treat the value as if it were `0` (this is noted in the [Calculating Freshness Lifetime](https:\/\/httpwg.org\/specs\/rfc9111.html#calculating.freshness.lifetime) section of the HTTP specification).\n\nhttp\n```\nCache-Control: max-age=604800\nAge: 100\n```\n#### `s-maxage`\nThe `s-maxage` response directive indicates how long the response remains [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) in a shared cache. The `s-maxage` directive is ignored by private caches, and overrides the value specified by the `max-age` directive or the `Expires` header for shared caches, if they are present.\n\nhttp\n```\nCache-Control: s-maxage=604800\n```\n#### `no-cache`\nThe `no-cache` response directive indicates that the response can be stored in caches, but the response must be validated with the origin server before each reuse, even when the cache is disconnected from the origin server.\n\nhttp\n```\nCache-Control: no-cache\n```\n\nIf you want caches to always check for content updates while reusing stored content, `no-cache` is the directive to use. It does this by requiring caches to revalidate each request with the origin server.\n\nNote that `no-cache` does not mean \"don't cache\". `no-cache` allows caches to store a response but requires them to revalidate it before reuse. If the sense of \"don't cache\" that you want is actually \"don't store\", then `no-store` is the directive to use.\n\n#### `must-revalidate`\nThe `must-revalidate` response directive indicates that the response can be stored in caches and can be reused while [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age). If the response becomes [stale](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age), it must be validated with the origin server before reuse.\n\nTypically, `must-revalidate` is used with `max-age`.\n\nhttp\n```\nCache-Control: max-age=604800, must-revalidate\n```\n\nHTTP allows caches to reuse [stale responses](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) when they are disconnected from the origin server. `must-revalidate` is a way to prevent this from happening - either the stored response is revalidated with the origin server or a 504 (Gateway Timeout) response is generated.\n\n#### `proxy-revalidate`\nThe `proxy-revalidate` response directive is the equivalent of `must-revalidate`, but specifically for shared caches only.\n\n#### `no-store`\nThe `no-store` response directive indicates that any caches of any kind (private or shared) should not store this response.\n\nhttp\n```\nCache-Control: no-store\n```\n#### `private`\nThe `private` response directive indicates that the response can be stored only in a private cache (e.g., local caches in browsers).\n\nhttp\n```\nCache-Control: private\n```\n\nYou should add the `private` directive for user-personalized content, especially for responses received after login and for sessions managed via cookies.\n\nIf you forget to add `private` to a response with personalized content, then that response can be stored in a shared cache and end up being reused for multiple users, which can cause personal information to leak.\n\n#### `public`\nThe `public` response directive indicates that the response can be stored in a shared cache. Responses for requests with `Authorization` header fields must not be stored in a shared cache; however, the `public` directive will cause such responses to be stored in a shared cache.\n\nhttp\n```\nCache-Control: public\n```\n\nIn general, when pages are under Basic Auth or Digest Auth, the browser sends requests with the `Authorization` header. This means that the response is access-controlled for restricted users (who have accounts), and it's fundamentally not shared-cacheable, even if it has `max-age`.\n\nYou can use the `public` directive to unlock that restriction.\n\nhttp\n```\nCache-Control: public, max-age=604800\n```\n\nNote that `s-maxage` or `must-revalidate` also unlock that restriction.\n\nIf a request doesn't have an `Authorization` header, or you are already using `s-maxage` or `must-revalidate` in the response, then you don't need to use `public`.\n\n#### `must-understand`\nThe `must-understand` response directive indicates that a cache should store the response only if it understands the requirements for caching based on status code.\n\n`must-understand` should be coupled with `no-store` for fallback behavior.\n\nhttp\n```\nCache-Control: must-understand, no-store\n```\n\nIf a cache doesn't support `must-understand`, it will be ignored. If `no-store` is also present, the response isn't stored.\n\nIf a cache supports `must-understand`, it stores the response with an understanding of cache requirements based on its status code.\n\n#### `no-transform`\nSome intermediaries transform content for various reasons. For example, some convert images to reduce transfer size. In some cases, this is undesirable for the content provider.\n\n`no-transform` indicates that any intermediary (regardless of whether it implements a cache) shouldn't transform the response contents.\n\n#### `immutable`\nThe `immutable` response directive indicates that the response will not be updated while it's [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age).\n\nhttp\n```\nCache-Control: public, max-age=604800, immutable\n```\n\nA modern best practice for static resources is to include version\/hashes in their URLs, while never modifying the resources — but instead, when necessary, *updating* the resources with newer versions that have new version-numbers\/hashes, so that their URLs are different. That's called the **cache-busting** pattern.\n\nhtml\n```\n<script src=\"https:\/\/example.com\/react.0.0.0.js\"><\/script>\n```\n\nWhen a user reloads the browser, the browser will send conditional requests for validating to the origin server. But it's not necessary to revalidate those kinds of static resources even when a user reloads the browser, because they're never modified. `immutable` tells a cache that the response is immutable while it's [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) and avoids those kinds of unnecessary conditional requests to the server.\n\nWhen you use a cache-busting pattern for resources and apply them to a long `max-age`, you can also add `immutable` to avoid revalidation.\n\n#### `stale-while-revalidate`\nThe `stale-while-revalidate` response directive indicates that the cache could reuse a stale response while it revalidates it to a cache.\n\nhttp\n```\nCache-Control: max-age=604800, stale-while-revalidate=86400\n```\n\nIn the example above, the response is [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) for 7 days (604800s). After 7 days it becomes [stale](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age), but the cache is allowed to reuse it for any requests that are made in the following day (86400s), provided that they revalidate the response in the background.\n\nRevalidation will make the cache be [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) again, so it appears to clients that it was always [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) during that period — effectively hiding the latency penalty of revalidation from them.\n\nIf no request happened during that period, the cache became [stale](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) and the next request will revalidate normally.\n\n#### `stale-if-error`\nThe `stale-if-error` response directive indicates that the cache can reuse a [stale response](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) when an upstream server generates an error, or when the error is generated locally. Here, an error is considered any response with a status code of 500, 502, 503, or 504.\n\nhttp\n```\nCache-Control: max-age=604800, stale-if-error=86400\n```\n\nIn the example above, the response is [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) for 7 days (604800s). Afterwards, it becomes [stale](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age), but can be used for an extra 1 day (86400s) when an error is encountered.\n\nAfter the stale-if-error period passes, the client will receive any error generated.\n\n### [Request Directives](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#request_directives)\n#### `no-cache`\nThe `no-cache` request directive asks caches to validate the response with the origin server before reuse.\n\nhttp\n```\nCache-Control: no-cache\n```\n\n`no-cache` allows clients to request the most up-to-date response even if the cache has a [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) response.\n\nBrowsers usually add `no-cache` to requests when users are **force reloading** a page.\n\n#### `no-store`\nThe `no-store` request directive allows a client to request that caches refrain from storing the request and corresponding response — even if the origin server's response could be stored.\n\nhttp\n```\nCache-Control: no-store\n```\n#### `max-age`\nThe `max-age=N` request directive indicates that the client allows a stored response that is generated on the origin server within *N* seconds — where *N* may be any non-negative integer (including `0`).\n\nhttp\n```\nCache-Control: max-age=10800\n```\n\nIn the case above, if the response with `Cache-Control: max-age=10800` was generated more than 3 hours ago (calculated from `max-age` and the `Age` header), the cache couldn't reuse that response.\n\nMany browsers use this directive for **reloading**, as explained below.\n\nhttp\n```\nCache-Control: max-age=0\n```\n\n`max-age=0` is a workaround for `no-cache`, because many old (HTTP\/1.0) cache implementations don't support `no-cache`. Recently browsers are still using `max-age=0` in \"reloading\" — for backward compatibility — and alternatively using `no-cache` to cause a \"force reloading\".\n\nIf the `max-age` value is negative (for example, `-1`) or isn't an integer (for example, `3599.99`), then the caching behavior is unspecified. Caches are encouraged to treat the value as if it were `0`.\n\n#### `max-stale`\nThe `max-stale=N` request directive indicates that the client allows a stored response that is [stale](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) within *N* seconds. If no *N* value is specified, the client will accept a stale response of any age.\n\nhttp\n```\nCache-Control: max-stale=3600\n```\n\nFor example, a request with the header above indicates that the browser will accept a stale response from the cache that has expired within the last hour.\n\nClients can use this header when the origin server is down or too slow and can accept cached responses from caches even if they are a bit old.\n\nNote that the major browsers do not support requests with `max-stale`.\n\n#### `min-fresh`\nThe `min-fresh=N` request directive indicates that the client allows a stored response that is [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) for at least *N* seconds.\n\nhttp\n```\nCache-Control: min-fresh=600\n```\n\nIn the case above, if the response with `Cache-Control: max-age=3600` was stored in caches 51 minutes ago, the cache couldn't reuse that response.\n\nClients can use this header when the user requires the response to not only be [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age), but also requires that it won't be updated for a period of time.\n\nNote that the major browsers do not support requests with `min-fresh`.\n\n#### `no-transform`\nSame meaning that `no-transform` has for a response, but for a request instead.\n\n#### `only-if-cached`\nThe client indicates that an already-cached response should be returned. If a cache has a stored response, even a stale one, it will be returned. If no cached response is available, a [504 Gateway Timeout](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Status\/504) response will be returned.\n\n#### `stale-if-error`\nThe `stale-if-error` request directive indicates that the browser is interested in receiving stale content on error from any intermediate server for a particular origin. This is not supported by any browser (see [Browser compatibility](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#browser_compatibility)).\n## [Use Cases](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#use_cases)\n### [Preventing storing](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#preventing_storing)\nIf you don't want a response stored in caches, use the `no-store` directive.\n\nhttp\n```\nCache-Control: no-store\n```\n\nNote that `no-cache` means \"it can be stored but don't reuse before validating\" — so it's not for preventing a response from being stored.\n\nhttp\n```\nCache-Control: no-cache\n```\n\nIn theory, if directives are conflicted, the most restrictive directive should be honored. So the example below is basically meaningless because `private`, `no-cache`, `max-age=0` and `must-revalidate` conflict with `no-store`.\n\nhttp\n```\n# conflicted\nCache-Control: private, no-cache, no-store, max-age=0, must-revalidate\n\n# equivalent to\nCache-Control: no-store\n```\n\n### [Caching static assets with \"cache busting\"](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#caching_static_assets_with_cache_busting)\nWhen you build static assets with versioning\/hashing mechanisms, adding a version\/hash to the filename or query string is a good way to manage caching.\n\nFor example:\n\nhtml\n```\n\n<script src=\"\/assets\/react.min.js\"><\/script>\n<img src=\"\/assets\/hero.png\" width=\"900\" height=\"400\" \/>\n```\n\nThe React library version will change when you update the library, and `hero.png` will also change when you edit the picture. So those are hard to store in a cache with `max-age`.\n\nIn such a case, you could address the caching needs by using a specific, numbered version of the library, and including the hash of the picture in its URL.\n\nhtml\n```\n\n<script src=\"\/assets\/react.0.0.0min.js\"><\/script>\n<img src=\"\/assets\/hero.png?hash=deadbeef\" width=\"900\" height=\"400\" \/>\n```\n\nYou can add a long `max-age` value and `immutable` because the content will never change.\n\nhttp\n```\n# \/assets\/*\nCache-Control: max-age=31536000, immutable\n```\n\nWhen you update the library or edit the picture, new content should have a new URL, and caches aren't reused. That is called the \"cache busting\" pattern.\n\nUse a `no-cache` to make sure that the HTML response itself is not cached. `no-cache` could cause revalidation, and the client will correctly receive a new version of the HTML response and static assets.\n\nhttp\n```\n# \/index.html\nCache-Control: no-cache\n```\n\nNote: If `index.html` is controlled under Basic Authentication or Digest Authentication, files under `\/assets` are not stored in the shared cache. If `\/assets\/` files are suitable for storing in a shared cache, you also need one of `public`, `s-maxage` or `must-revalidate`.\n\n### [Up-to-date contents always](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#up-to-date_contents_always)\nFor content that's generated dynamically, or that's static but updated often, you want a user to always receive the most up-to-date version.\n\nIf you don't add a `Cache-Control` header because the response is not intended to be cached, that could cause an unexpected result. Cache storage is allowed to cache it heuristically — so if you have any requirements on caching, you should always indicate them explicitly, in the `Cache-Control` header.\n\nAdding `no-cache` to the response causes revalidation to the server, so you can serve a [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) response every time — or if the client already has a new one, just respond `304 Not Modified`.\n\nhttp\n```\nCache-Control: no-cache\n```\n\nMost HTTP\/1.0 caches don't support `no-cache` directives, so historically `max-age=0` was used as a workaround. But only `max-age=0` could cause a [stale response](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) to be reused when caches disconnected from the origin server. `must-revalidate` addresses that. That's why the example below is equivalent to `no-cache`.\n\nhttp\n```\nCache-Control: max-age=0, must-revalidate\n```\n\nBut for now, you can simply use `no-cache` instead.\n\n### [Clearing an already-stored cache](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#clearing_an_already-stored_cache)\nThere are no cache directives for clearing already-stored responses from caches on *intermediate* servers.\n\nImagine that clients\/caches store a [fresh](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching#fresh_and_stale_based_on_age) response for a path, with no request flight to the server. There is nothing a server could do to that path.\n\n[`Clear-Site-Data: cache`](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Clear-Site-Data#cache) can be used to clear every stored response for a site in the browser cache, so use this with care. Note that this will not affect shared or intermediate caches.\n\n## [Specifications](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#specifications)\n| Specification |\n|---|\n| [HTTP Caching \\# field.cache-control](https:\/\/httpwg.org\/specs\/rfc9111.html#field.cache-control) |\n| [HTTP Immutable Responses \\# the-immutable-cache-control-extension](https:\/\/httpwg.org\/specs\/rfc8246.html#the-immutable-cache-control-extension) |\n## [Browser compatibility](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#browser_compatibility)\n## [See also](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Reference\/Headers\/Cache-Control#see_also)\n- [HTTP caching](https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/HTTP\/Guides\/Caching)\n- [Caching Tutorial for Web Authors and Webmasters](https:\/\/www.mnot.net\/cache_docs\/)\n- [Caching best practices & max-age gotchas](https:\/\/jakearchibald.com\/2016\/caching-best-practices\/)\n- [Cache-Control for Civilians](https:\/\/csswizardry.com\/2019\/03\/cache-control-for-civilians\/)\n- [RFC 9111 – HTTP Caching](https:\/\/httpwg.org\/specs\/rfc9111.html)\n- [RFC 5861 – HTTP Cache-Control Extensions for Stale Content](https:\/\/httpwg.org\/specs\/rfc5861.html)\n- [RFC 8246 – HTTP Immutable Responses](https:\/\/httpwg.org\/specs\/rfc8246.html)","meta_canonical":null}

3. Robots.txt Check

Query:

Response:

4. Spam/Ban Check

Query:

Response:

5. Seen Status Check

ℹ️ Skipped - page is already crawled

📄

INDEXABLE

✅

CRAWLED

15 hours ago

🤖

ROBOTS ALLOWED

Page Info Filters

Filter	Status	Condition	Details
HTTP status	PASS	`download_http_code = 200`	HTTP 200
Age cutoff	PASS	`download_stamp > now() - 6 MONTH`	0 months ago
History drop	PASS	`isNull(history_drop_reason)`	No drop reason
Spam/ban	PASS	`fh_dont_index != 1 AND ml_spam_score = 0`	ml_spam_score=0
Canonical	PASS	`meta_canonical IS NULL OR = '' OR = src_unparsed`	Not set

Page Details

Property	Value
URL	https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control
Last Crawled	2026-04-11 10:50:13 (15 hours ago)
First Indexed	2025-03-14 01:07:15 (1 year ago)
HTTP Status Code	200
Meta Title	Cache-Control header - HTTP \| MDN
Meta Description	The HTTP Cache-Control header holds directives (instructions) in both requests and responses that control caching in browsers and shared caches (e.g., Proxies, CDNs).
Meta Canonical	null
Boilerpipe Text	Syntax http Cache-Control: <directive>, <directive>, ... Cache directives follow these rules: Caching directives are case-insensitive. However, lowercase is recommended because some implementations do not recognize uppercase directives. Multiple directives are permitted and must be comma-separated (e.g., Cache-control: max-age=180, public ). Some directives have an optional argument. When an argument is provided, it is separated from the directive name by an equals symbol ( = ). Typically, arguments for the directives are integers and are therefore not enclosed in quote characters (e.g., Cache-control: max-age=12 ). Cache directives The following table lists the standard Cache-Control directives: Request Response max-age max-age max-stale - min-fresh - - s-maxage no-cache no-cache no-store no-store no-transform no-transform only-if-cached - - must-revalidate - proxy-revalidate - must-understand - private - public - immutable - stale-while-revalidate stale-if-error stale-if-error Note: Check the compatibility table for their support; user agents that don't recognize them should ignore them. Vocabulary This section defines the terms used in this document, some of which are from the specification. (HTTP) cache Implementation that holds requests and responses for reusing in subsequent requests. It can be either a shared cache or a private cache. Shared cache Cache that exists between the origin server and clients (e.g., Proxy, CDN). It stores a single response and reuses it with multiple users — so developers should avoid storing personalized contents to be cached in the shared cache. Private cache Cache that exists in the client. It is also called local cache or browser cache . It can store and reuse personalized content for a single user. Store response Store a response in caches when the response is cacheable. However, the cached response is not always reused as-is. (Usually, "cache" means storing a response.) Reuse response Reuse cached responses for subsequent requests. Revalidate response Ask the origin server whether or not the stored response is still fresh . Usually, the revalidation is done through a conditional request. Fresh response Indicates that the response is fresh . This usually means the response can be reused for subsequent requests, depending on request directives. Stale response Indicates that the response is a stale response . This usually means the response can't be reused as-is. Cache storage isn't required to remove stale responses immediately because revalidation could change the response from being stale to being fresh again. Age The time since a response was generated. It is a criterion for whether a response is fresh or stale . Directives This section lists directives that affect caching — both response directives and request directives. Response Directives max-age The max-age=N response directive indicates that the response remains fresh until N seconds after the response is generated. http Cache-Control: max-age=604800 Indicates that caches can store this response and reuse it for subsequent requests while it's fresh . Note that max-age is not the elapsed time since the response was received; it is the elapsed time since the response was generated on the origin server. So if the other cache(s) — on the network route taken by the response — store the response for 100 seconds (indicated using the Age response header field), the browser cache would deduct 100 seconds from its freshness lifetime . If the max-age value is negative (for example, -1 ) or isn't an integer (for example, 3599.99 ), then the caching behavior is unspecified. Caches are encouraged to treat the value as if it were 0 (this is noted in the Calculating Freshness Lifetime section of the HTTP specification). http Cache-Control: max-age=604800 Age: 100 s-maxage The s-maxage response directive indicates how long the response remains fresh in a shared cache. The s-maxage directive is ignored by private caches, and overrides the value specified by the max-age directive or the Expires header for shared caches, if they are present. http Cache-Control: s-maxage=604800 no-cache The no-cache response directive indicates that the response can be stored in caches, but the response must be validated with the origin server before each reuse, even when the cache is disconnected from the origin server. http Cache-Control: no-cache If you want caches to always check for content updates while reusing stored content, no-cache is the directive to use. It does this by requiring caches to revalidate each request with the origin server. Note that no-cache does not mean "don't cache". no-cache allows caches to store a response but requires them to revalidate it before reuse. If the sense of "don't cache" that you want is actually "don't store", then no-store is the directive to use. must-revalidate The must-revalidate response directive indicates that the response can be stored in caches and can be reused while fresh . If the response becomes stale , it must be validated with the origin server before reuse. Typically, must-revalidate is used with max-age . http Cache-Control: max-age=604800, must-revalidate HTTP allows caches to reuse stale responses when they are disconnected from the origin server. must-revalidate is a way to prevent this from happening - either the stored response is revalidated with the origin server or a 504 (Gateway Timeout) response is generated. proxy-revalidate The proxy-revalidate response directive is the equivalent of must-revalidate , but specifically for shared caches only. no-store The no-store response directive indicates that any caches of any kind (private or shared) should not store this response. http Cache-Control: no-store private The private response directive indicates that the response can be stored only in a private cache (e.g., local caches in browsers). http Cache-Control: private You should add the private directive for user-personalized content, especially for responses received after login and for sessions managed via cookies. If you forget to add private to a response with personalized content, then that response can be stored in a shared cache and end up being reused for multiple users, which can cause personal information to leak. public The public response directive indicates that the response can be stored in a shared cache. Responses for requests with Authorization header fields must not be stored in a shared cache; however, the public directive will cause such responses to be stored in a shared cache. http Cache-Control: public In general, when pages are under Basic Auth or Digest Auth, the browser sends requests with the Authorization header. This means that the response is access-controlled for restricted users (who have accounts), and it's fundamentally not shared-cacheable, even if it has max-age . You can use the public directive to unlock that restriction. http Cache-Control: public, max-age=604800 Note that s-maxage or must-revalidate also unlock that restriction. If a request doesn't have an Authorization header, or you are already using s-maxage or must-revalidate in the response, then you don't need to use public . must-understand The must-understand response directive indicates that a cache should store the response only if it understands the requirements for caching based on status code. must-understand should be coupled with no-store for fallback behavior. http Cache-Control: must-understand, no-store If a cache doesn't support must-understand , it will be ignored. If no-store is also present, the response isn't stored. If a cache supports must-understand , it stores the response with an understanding of cache requirements based on its status code. no-transform Some intermediaries transform content for various reasons. For example, some convert images to reduce transfer size. In some cases, this is undesirable for the content provider. no-transform indicates that any intermediary (regardless of whether it implements a cache) shouldn't transform the response contents. immutable The immutable response directive indicates that the response will not be updated while it's fresh . http Cache-Control: public, max-age=604800, immutable A modern best practice for static resources is to include version/hashes in their URLs, while never modifying the resources — but instead, when necessary, updating the resources with newer versions that have new version-numbers/hashes, so that their URLs are different. That's called the cache-busting pattern. html <script src="https://example.com/react.0.0.0.js"></script> When a user reloads the browser, the browser will send conditional requests for validating to the origin server. But it's not necessary to revalidate those kinds of static resources even when a user reloads the browser, because they're never modified. immutable tells a cache that the response is immutable while it's fresh and avoids those kinds of unnecessary conditional requests to the server. When you use a cache-busting pattern for resources and apply them to a long max-age , you can also add immutable to avoid revalidation. stale-while-revalidate The stale-while-revalidate response directive indicates that the cache could reuse a stale response while it revalidates it to a cache. http Cache-Control: max-age=604800, stale-while-revalidate=86400 In the example above, the response is fresh for 7 days (604800s). After 7 days it becomes stale , but the cache is allowed to reuse it for any requests that are made in the following day (86400s), provided that they revalidate the response in the background. Revalidation will make the cache be fresh again, so it appears to clients that it was always fresh during that period — effectively hiding the latency penalty of revalidation from them. If no request happened during that period, the cache became stale and the next request will revalidate normally. stale-if-error The stale-if-error response directive indicates that the cache can reuse a stale response when an upstream server generates an error, or when the error is generated locally. Here, an error is considered any response with a status code of 500, 502, 503, or 504. http Cache-Control: max-age=604800, stale-if-error=86400 In the example above, the response is fresh for 7 days (604800s). Afterwards, it becomes stale , but can be used for an extra 1 day (86400s) when an error is encountered. After the stale-if-error period passes, the client will receive any error generated. Request Directives no-cache The no-cache request directive asks caches to validate the response with the origin server before reuse. http Cache-Control: no-cache no-cache allows clients to request the most up-to-date response even if the cache has a fresh response. Browsers usually add no-cache to requests when users are force reloading a page. no-store The no-store request directive allows a client to request that caches refrain from storing the request and corresponding response — even if the origin server's response could be stored. http Cache-Control: no-store max-age The max-age=N request directive indicates that the client allows a stored response that is generated on the origin server within N seconds — where N may be any non-negative integer (including 0 ). http Cache-Control: max-age=10800 In the case above, if the response with Cache-Control: max-age=10800 was generated more than 3 hours ago (calculated from max-age and the Age header), the cache couldn't reuse that response. Many browsers use this directive for reloading , as explained below. http Cache-Control: max-age=0 max-age=0 is a workaround for no-cache , because many old (HTTP/1.0) cache implementations don't support no-cache . Recently browsers are still using max-age=0 in "reloading" — for backward compatibility — and alternatively using no-cache to cause a "force reloading". If the max-age value is negative (for example, -1 ) or isn't an integer (for example, 3599.99 ), then the caching behavior is unspecified. Caches are encouraged to treat the value as if it were 0 . max-stale The max-stale=N request directive indicates that the client allows a stored response that is stale within N seconds. If no N value is specified, the client will accept a stale response of any age. http Cache-Control: max-stale=3600 For example, a request with the header above indicates that the browser will accept a stale response from the cache that has expired within the last hour. Clients can use this header when the origin server is down or too slow and can accept cached responses from caches even if they are a bit old. Note that the major browsers do not support requests with max-stale . min-fresh The min-fresh=N request directive indicates that the client allows a stored response that is fresh for at least N seconds. http Cache-Control: min-fresh=600 In the case above, if the response with Cache-Control: max-age=3600 was stored in caches 51 minutes ago, the cache couldn't reuse that response. Clients can use this header when the user requires the response to not only be fresh , but also requires that it won't be updated for a period of time. Note that the major browsers do not support requests with min-fresh . no-transform Same meaning that no-transform has for a response, but for a request instead. only-if-cached The client indicates that an already-cached response should be returned. If a cache has a stored response, even a stale one, it will be returned. If no cached response is available, a 504 Gateway Timeout response will be returned. stale-if-error The stale-if-error request directive indicates that the browser is interested in receiving stale content on error from any intermediate server for a particular origin. This is not supported by any browser (see Browser compatibility ). Use Cases Preventing storing If you don't want a response stored in caches, use the no-store directive. http Cache-Control: no-store Note that no-cache means "it can be stored but don't reuse before validating" — so it's not for preventing a response from being stored. http Cache-Control: no-cache In theory, if directives are conflicted, the most restrictive directive should be honored. So the example below is basically meaningless because private , no-cache , max-age=0 and must-revalidate conflict with no-store . http # conflicted Cache-Control: private, no-cache, no-store, max-age=0, must-revalidate # equivalent to Cache-Control: no-store Caching static assets with "cache busting" When you build static assets with versioning/hashing mechanisms, adding a version/hash to the filename or query string is a good way to manage caching. For example: html <!-- index.html --> <script src="/assets/react.min.js"></script> <img src="/assets/hero.png" width="900" height="400" /> The React library version will change when you update the library, and hero.png will also change when you edit the picture. So those are hard to store in a cache with max-age . In such a case, you could address the caching needs by using a specific, numbered version of the library, and including the hash of the picture in its URL. html <!-- index.html --> <script src="/assets/react.0.0.0min.js"></script> <img src="/assets/hero.png?hash=deadbeef" width="900" height="400" /> You can add a long max-age value and immutable because the content will never change. http # /assets/* Cache-Control: max-age=31536000, immutable When you update the library or edit the picture, new content should have a new URL, and caches aren't reused. That is called the "cache busting" pattern. Use a no-cache to make sure that the HTML response itself is not cached. no-cache could cause revalidation, and the client will correctly receive a new version of the HTML response and static assets. http # /index.html Cache-Control: no-cache Note: If index.html is controlled under Basic Authentication or Digest Authentication, files under /assets are not stored in the shared cache. If /assets/ files are suitable for storing in a shared cache, you also need one of public , s-maxage or must-revalidate . Up-to-date contents always For content that's generated dynamically, or that's static but updated often, you want a user to always receive the most up-to-date version. If you don't add a Cache-Control header because the response is not intended to be cached, that could cause an unexpected result. Cache storage is allowed to cache it heuristically — so if you have any requirements on caching, you should always indicate them explicitly, in the Cache-Control header. Adding no-cache to the response causes revalidation to the server, so you can serve a fresh response every time — or if the client already has a new one, just respond 304 Not Modified . http Cache-Control: no-cache Most HTTP/1.0 caches don't support no-cache directives, so historically max-age=0 was used as a workaround. But only max-age=0 could cause a stale response to be reused when caches disconnected from the origin server. must-revalidate addresses that. That's why the example below is equivalent to no-cache . http Cache-Control: max-age=0, must-revalidate But for now, you can simply use no-cache instead. Clearing an already-stored cache There are no cache directives for clearing already-stored responses from caches on intermediate servers. Imagine that clients/caches store a fresh response for a path, with no request flight to the server. There is nothing a server could do to that path. Clear-Site-Data: cache can be used to clear every stored response for a site in the browser cache, so use this with care. Note that this will not affect shared or intermediate caches. Specifications Specification HTTP Caching # field.cache-control HTTP Immutable Responses # the-immutable-cache-control-extension Browser compatibility See also HTTP caching Caching Tutorial for Web Authors and Webmasters Caching best practices & max-age gotchas Cache-Control for Civilians RFC 9111 – HTTP Caching RFC 5861 – HTTP Cache-Control Extensions for Stale Content RFC 8246 – HTTP Immutable Responses
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[Web](https://developer.mozilla.org/en-US/docs/Web) 2. [HTTP](https://developer.mozilla.org/en-US/docs/Web/HTTP) 3. [Reference](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference) 4. [Headers](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers) 5. [Cache-Control](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control) # Cache-Control header Baseline Widely available This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015. - [Learn more](https://developer.mozilla.org/en-US/docs/Glossary/Baseline/Compatibility) - [See full compatibility](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#browser_compatibility) - [Report feedback](https://survey.alchemer.com/s3/7634825/MDN-baseline-feedback?page=%2Fen-US%2Fdocs%2FWeb%2FHTTP%2FReference%2FHeaders%2FCache-Control&level=high) The HTTP `Cache-Control` header holds directives (instructions) in both requests and responses that control [caching](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching) in browsers and shared caches (e.g., Proxies, CDNs). \| \| \| \|---\|---\| \| Header type \| [Request header](https://developer.mozilla.org/en-US/docs/Glossary/Request_header), [Response header](https://developer.mozilla.org/en-US/docs/Glossary/Response_header) \| \| [Forbidden request header](https://developer.mozilla.org/en-US/docs/Glossary/Forbidden_request_header) \| No \| \| [CORS-safelisted response header](https://developer.mozilla.org/en-US/docs/Glossary/CORS-safelisted_response_header) \| Yes \| ## In this article - [Syntax](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#syntax) - [Vocabulary](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#vocabulary) - [Directives](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#directives) - [Use Cases](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#use_cases) - [Specifications](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#specifications) - [Browser compatibility](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#browser_compatibility) - [See also](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#see_also) ## [Syntax](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#syntax) http ``` Cache-Control: <directive>, <directive>, ... ``` Cache directives follow these rules: - Caching directives are case-insensitive. However, lowercase is recommended because some implementations do not recognize uppercase directives. - Multiple directives are permitted and must be comma-separated (e.g., `Cache-control: max-age=180, public`). - Some directives have an optional argument. When an argument is provided, it is separated from the directive name by an equals symbol (`=`). Typically, arguments for the directives are integers and are therefore not enclosed in quote characters (e.g., `Cache-control: max-age=12`). ### [Cache directives](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#cache_directives) The following table lists the standard `Cache-Control` directives: \| Request \| Response \| \|---\|---\| \| `max-age` \| `max-age` \| \| `max-stale` \| \- \| \| `min-fresh` \| \- \| \| \- \| `s-maxage` \| \| `no-cache` \| `no-cache` \| \| `no-store` \| `no-store` \| \| `no-transform` \| `no-transform` \| \| `only-if-cached` \| \- \| \| \- \| `must-revalidate` \| \| \- \| `proxy-revalidate` \| \| \- \| `must-understand` \| \| \- \| `private` \| \| \- \| `public` \| \| \- \| `immutable` \| \| \- \| `stale-while-revalidate` \| \| `stale-if-error` \| `stale-if-error` \| Note: Check the [compatibility table](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#browser_compatibility) for their support; user agents that don't recognize them should ignore them. ## [Vocabulary](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#vocabulary) This section defines the terms used in this document, some of which are from the specification. [(HTTP) cache](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#http_cache) Implementation that holds requests and responses for reusing in subsequent requests. It can be either a shared cache or a private cache. [Shared cache](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#shared_cache) Cache that exists between the origin server and clients (e.g., Proxy, CDN). It stores a single response and reuses it with multiple users — so developers should avoid storing personalized contents to be cached in the shared cache. [Private cache](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#private_cache) Cache that exists in the client. It is also called local cache or browser cache. It can store and reuse personalized content for a single user. [Store response](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#store_response) Store a response in caches when the response is cacheable. However, the cached response is not always reused as-is. (Usually, "cache" means storing a response.) [Reuse response](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#reuse_response) Reuse cached responses for subsequent requests. [Revalidate response](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#revalidate_response) Ask the origin server whether or not the stored response is still [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age). Usually, the revalidation is done through a conditional request. [Fresh response](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#fresh_response) Indicates that the response is [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age). This usually means the response can be reused for subsequent requests, depending on request directives. [Stale response](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#stale_response) Indicates that the response is a [stale response](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age). This usually means the response can't be reused as-is. Cache storage isn't required to remove stale responses immediately because revalidation could change the response from being stale to being [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) again. [Age](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#age) The time since a response was generated. It is a criterion for whether a response is [fresh or stale](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age). ## [Directives](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#directives) This section lists directives that affect caching — both response directives and request directives. ### [Response Directives](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#response_directives) #### `max-age` The `max-age=N` response directive indicates that the response remains [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) until N seconds after the response is generated. http ``` Cache-Control: max-age=604800 ``` Indicates that caches can store this response and reuse it for subsequent requests while it's [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age). Note that `max-age` is not the elapsed time since the response was received; it is the elapsed time since the response was generated on the origin server. So if the other cache(s) — on the network route taken by the response — store the response for 100 seconds (indicated using the `Age` response header field), the browser cache would deduct 100 seconds from its [freshness lifetime](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age). If the `max-age` value is negative (for example, `-1`) or isn't an integer (for example, `3599.99`), then the caching behavior is unspecified. Caches are encouraged to treat the value as if it were `0` (this is noted in the [Calculating Freshness Lifetime](https://httpwg.org/specs/rfc9111.html#calculating.freshness.lifetime) section of the HTTP specification). http ``` Cache-Control: max-age=604800 Age: 100 ``` #### `s-maxage` The `s-maxage` response directive indicates how long the response remains [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) in a shared cache. The `s-maxage` directive is ignored by private caches, and overrides the value specified by the `max-age` directive or the `Expires` header for shared caches, if they are present. http ``` Cache-Control: s-maxage=604800 ``` #### `no-cache` The `no-cache` response directive indicates that the response can be stored in caches, but the response must be validated with the origin server before each reuse, even when the cache is disconnected from the origin server. http ``` Cache-Control: no-cache ``` If you want caches to always check for content updates while reusing stored content, `no-cache` is the directive to use. It does this by requiring caches to revalidate each request with the origin server. Note that `no-cache` does not mean "don't cache". `no-cache` allows caches to store a response but requires them to revalidate it before reuse. If the sense of "don't cache" that you want is actually "don't store", then `no-store` is the directive to use. #### `must-revalidate` The `must-revalidate` response directive indicates that the response can be stored in caches and can be reused while [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age). If the response becomes [stale](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age), it must be validated with the origin server before reuse. Typically, `must-revalidate` is used with `max-age`. http ``` Cache-Control: max-age=604800, must-revalidate ``` HTTP allows caches to reuse [stale responses](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) when they are disconnected from the origin server. `must-revalidate` is a way to prevent this from happening - either the stored response is revalidated with the origin server or a 504 (Gateway Timeout) response is generated. #### `proxy-revalidate` The `proxy-revalidate` response directive is the equivalent of `must-revalidate`, but specifically for shared caches only. #### `no-store` The `no-store` response directive indicates that any caches of any kind (private or shared) should not store this response. http ``` Cache-Control: no-store ``` #### `private` The `private` response directive indicates that the response can be stored only in a private cache (e.g., local caches in browsers). http ``` Cache-Control: private ``` You should add the `private` directive for user-personalized content, especially for responses received after login and for sessions managed via cookies. If you forget to add `private` to a response with personalized content, then that response can be stored in a shared cache and end up being reused for multiple users, which can cause personal information to leak. #### `public` The `public` response directive indicates that the response can be stored in a shared cache. Responses for requests with `Authorization` header fields must not be stored in a shared cache; however, the `public` directive will cause such responses to be stored in a shared cache. http ``` Cache-Control: public ``` In general, when pages are under Basic Auth or Digest Auth, the browser sends requests with the `Authorization` header. This means that the response is access-controlled for restricted users (who have accounts), and it's fundamentally not shared-cacheable, even if it has `max-age`. You can use the `public` directive to unlock that restriction. http ``` Cache-Control: public, max-age=604800 ``` Note that `s-maxage` or `must-revalidate` also unlock that restriction. If a request doesn't have an `Authorization` header, or you are already using `s-maxage` or `must-revalidate` in the response, then you don't need to use `public`. #### `must-understand` The `must-understand` response directive indicates that a cache should store the response only if it understands the requirements for caching based on status code. `must-understand` should be coupled with `no-store` for fallback behavior. http ``` Cache-Control: must-understand, no-store ``` If a cache doesn't support `must-understand`, it will be ignored. If `no-store` is also present, the response isn't stored. If a cache supports `must-understand`, it stores the response with an understanding of cache requirements based on its status code. #### `no-transform` Some intermediaries transform content for various reasons. For example, some convert images to reduce transfer size. In some cases, this is undesirable for the content provider. `no-transform` indicates that any intermediary (regardless of whether it implements a cache) shouldn't transform the response contents. #### `immutable` The `immutable` response directive indicates that the response will not be updated while it's [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age). http ``` Cache-Control: public, max-age=604800, immutable ``` A modern best practice for static resources is to include version/hashes in their URLs, while never modifying the resources — but instead, when necessary, updating the resources with newer versions that have new version-numbers/hashes, so that their URLs are different. That's called the cache-busting pattern. html ``` <script src="https://example.com/react.0.0.0.js"></script> ``` When a user reloads the browser, the browser will send conditional requests for validating to the origin server. But it's not necessary to revalidate those kinds of static resources even when a user reloads the browser, because they're never modified. `immutable` tells a cache that the response is immutable while it's [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) and avoids those kinds of unnecessary conditional requests to the server. When you use a cache-busting pattern for resources and apply them to a long `max-age`, you can also add `immutable` to avoid revalidation. #### `stale-while-revalidate` The `stale-while-revalidate` response directive indicates that the cache could reuse a stale response while it revalidates it to a cache. http ``` Cache-Control: max-age=604800, stale-while-revalidate=86400 ``` In the example above, the response is [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) for 7 days (604800s). After 7 days it becomes [stale](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age), but the cache is allowed to reuse it for any requests that are made in the following day (86400s), provided that they revalidate the response in the background. Revalidation will make the cache be [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) again, so it appears to clients that it was always [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) during that period — effectively hiding the latency penalty of revalidation from them. If no request happened during that period, the cache became [stale](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) and the next request will revalidate normally. #### `stale-if-error` The `stale-if-error` response directive indicates that the cache can reuse a [stale response](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) when an upstream server generates an error, or when the error is generated locally. Here, an error is considered any response with a status code of 500, 502, 503, or 504. http ``` Cache-Control: max-age=604800, stale-if-error=86400 ``` In the example above, the response is [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) for 7 days (604800s). Afterwards, it becomes [stale](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age), but can be used for an extra 1 day (86400s) when an error is encountered. After the stale-if-error period passes, the client will receive any error generated. ### [Request Directives](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#request_directives) #### `no-cache` The `no-cache` request directive asks caches to validate the response with the origin server before reuse. http ``` Cache-Control: no-cache ``` `no-cache` allows clients to request the most up-to-date response even if the cache has a [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) response. Browsers usually add `no-cache` to requests when users are force reloading a page. #### `no-store` The `no-store` request directive allows a client to request that caches refrain from storing the request and corresponding response — even if the origin server's response could be stored. http ``` Cache-Control: no-store ``` #### `max-age` The `max-age=N` request directive indicates that the client allows a stored response that is generated on the origin server within N seconds — where N may be any non-negative integer (including `0`). http ``` Cache-Control: max-age=10800 ``` In the case above, if the response with `Cache-Control: max-age=10800` was generated more than 3 hours ago (calculated from `max-age` and the `Age` header), the cache couldn't reuse that response. Many browsers use this directive for reloading, as explained below. http ``` Cache-Control: max-age=0 ``` `max-age=0` is a workaround for `no-cache`, because many old (HTTP/1.0) cache implementations don't support `no-cache`. Recently browsers are still using `max-age=0` in "reloading" — for backward compatibility — and alternatively using `no-cache` to cause a "force reloading". If the `max-age` value is negative (for example, `-1`) or isn't an integer (for example, `3599.99`), then the caching behavior is unspecified. Caches are encouraged to treat the value as if it were `0`. #### `max-stale` The `max-stale=N` request directive indicates that the client allows a stored response that is [stale](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) within N seconds. If no N value is specified, the client will accept a stale response of any age. http ``` Cache-Control: max-stale=3600 ``` For example, a request with the header above indicates that the browser will accept a stale response from the cache that has expired within the last hour. Clients can use this header when the origin server is down or too slow and can accept cached responses from caches even if they are a bit old. Note that the major browsers do not support requests with `max-stale`. #### `min-fresh` The `min-fresh=N` request directive indicates that the client allows a stored response that is [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) for at least N seconds. http ``` Cache-Control: min-fresh=600 ``` In the case above, if the response with `Cache-Control: max-age=3600` was stored in caches 51 minutes ago, the cache couldn't reuse that response. Clients can use this header when the user requires the response to not only be [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age), but also requires that it won't be updated for a period of time. Note that the major browsers do not support requests with `min-fresh`. #### `no-transform` Same meaning that `no-transform` has for a response, but for a request instead. #### `only-if-cached` The client indicates that an already-cached response should be returned. If a cache has a stored response, even a stale one, it will be returned. If no cached response is available, a [504 Gateway Timeout](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/504) response will be returned. #### `stale-if-error` The `stale-if-error` request directive indicates that the browser is interested in receiving stale content on error from any intermediate server for a particular origin. This is not supported by any browser (see [Browser compatibility](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#browser_compatibility)). ## [Use Cases](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#use_cases) ### [Preventing storing](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#preventing_storing) If you don't want a response stored in caches, use the `no-store` directive. http ``` Cache-Control: no-store ``` Note that `no-cache` means "it can be stored but don't reuse before validating" — so it's not for preventing a response from being stored. http ``` Cache-Control: no-cache ``` In theory, if directives are conflicted, the most restrictive directive should be honored. So the example below is basically meaningless because `private`, `no-cache`, `max-age=0` and `must-revalidate` conflict with `no-store`. http ``` # conflicted Cache-Control: private, no-cache, no-store, max-age=0, must-revalidate # equivalent to Cache-Control: no-store ``` ### [Caching static assets with "cache busting"](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#caching_static_assets_with_cache_busting) When you build static assets with versioning/hashing mechanisms, adding a version/hash to the filename or query string is a good way to manage caching. For example: html ``` <!-- index.html --> <script src="/assets/react.min.js"></script> <img src="/assets/hero.png" width="900" height="400" /> ``` The React library version will change when you update the library, and `hero.png` will also change when you edit the picture. So those are hard to store in a cache with `max-age`. In such a case, you could address the caching needs by using a specific, numbered version of the library, and including the hash of the picture in its URL. html ``` <!-- index.html --> <script src="/assets/react.0.0.0min.js"></script> <img src="/assets/hero.png?hash=deadbeef" width="900" height="400" /> ``` You can add a long `max-age` value and `immutable` because the content will never change. http ``` # /assets/* Cache-Control: max-age=31536000, immutable ``` When you update the library or edit the picture, new content should have a new URL, and caches aren't reused. That is called the "cache busting" pattern. Use a `no-cache` to make sure that the HTML response itself is not cached. `no-cache` could cause revalidation, and the client will correctly receive a new version of the HTML response and static assets. http ``` # /index.html Cache-Control: no-cache ``` Note: If `index.html` is controlled under Basic Authentication or Digest Authentication, files under `/assets` are not stored in the shared cache. If `/assets/` files are suitable for storing in a shared cache, you also need one of `public`, `s-maxage` or `must-revalidate`. ### [Up-to-date contents always](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#up-to-date_contents_always) For content that's generated dynamically, or that's static but updated often, you want a user to always receive the most up-to-date version. If you don't add a `Cache-Control` header because the response is not intended to be cached, that could cause an unexpected result. Cache storage is allowed to cache it heuristically — so if you have any requirements on caching, you should always indicate them explicitly, in the `Cache-Control` header. Adding `no-cache` to the response causes revalidation to the server, so you can serve a [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) response every time — or if the client already has a new one, just respond `304 Not Modified`. http ``` Cache-Control: no-cache ``` Most HTTP/1.0 caches don't support `no-cache` directives, so historically `max-age=0` was used as a workaround. But only `max-age=0` could cause a [stale response](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) to be reused when caches disconnected from the origin server. `must-revalidate` addresses that. That's why the example below is equivalent to `no-cache`. http ``` Cache-Control: max-age=0, must-revalidate ``` But for now, you can simply use `no-cache` instead. ### [Clearing an already-stored cache](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#clearing_an_already-stored_cache) There are no cache directives for clearing already-stored responses from caches on intermediate servers. Imagine that clients/caches store a [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) response for a path, with no request flight to the server. There is nothing a server could do to that path. [`Clear-Site-Data: cache`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Clear-Site-Data#cache) can be used to clear every stored response for a site in the browser cache, so use this with care. Note that this will not affect shared or intermediate caches. ## [Specifications](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#specifications) \| Specification \| \|---\| \| [HTTP Caching \# field.cache-control](https://httpwg.org/specs/rfc9111.html#field.cache-control) \| \| [HTTP Immutable Responses \# the-immutable-cache-control-extension](https://httpwg.org/specs/rfc8246.html#the-immutable-cache-control-extension) \| ## [Browser compatibility](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#browser_compatibility) ## [See also](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#see_also) - [HTTP caching](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching) - [Caching Tutorial for Web Authors and Webmasters](https://www.mnot.net/cache_docs/) - [Caching best practices & max-age gotchas](https://jakearchibald.com/2016/caching-best-practices/) - [Cache-Control for Civilians](https://csswizardry.com/2019/03/cache-control-for-civilians/) - [RFC 9111 – HTTP Caching](https://httpwg.org/specs/rfc9111.html) - [RFC 5861 – HTTP Cache-Control Extensions for Stale Content](https://httpwg.org/specs/rfc5861.html) - [RFC 8246 – HTTP Immutable Responses](https://httpwg.org/specs/rfc8246.html) ## Help improve MDN [Learn how to contribute](https://developer.mozilla.org/en-US/docs/MDN/Community/Getting_started) This page was last modified on Nov 16, 2025 by [MDN contributors](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control/contributors.txt). [View this page on GitHub](https://github.com/mdn/content/blob/main/files/en-us/web/http/reference/headers/cache-control/index.md?plain=1 "Folder: en-us/web/http/reference/headers/cache-control (Opens in a new tab)") • [Report a problem with this content](https://github.com/mdn/content/issues/new?template=page-report.yml&mdn-url=https%3A%2F%2Fdeveloper.mozilla.org%2Fen-US%2Fdocs%2FWeb%2FHTTP%2FReference%2FHeaders%2FCache-Control&metadata=%3C%21--+Do+not+make+changes+below+this+line+--%3E%0A%3Cdetails%3E%0A%3Csummary%3EPage+report+details%3C%2Fsummary%3E%0A%0A+Folder%3A+%60en-us%2Fweb%2Fhttp%2Freference%2Fheaders%2Fcache-control%60%0A+MDN+URL%3A+https%3A%2F%2Fdeveloper.mozilla.org%2Fen-US%2Fdocs%2FWeb%2FHTTP%2FReference%2FHeaders%2FCache-Control%0A+GitHub+URL%3A+https%3A%2F%2Fgithub.com%2Fmdn%2Fcontent%2Fblob%2Fmain%2Ffiles%2Fen-us%2Fweb%2Fhttp%2Freference%2Fheaders%2Fcache-control%2Findex.md%0A+Last+commit%3A+https%3A%2F%2Fgithub.com%2Fmdn%2Fcontent%2Fcommit%2Ffd4cf672d03417a8a391a74db10dfda3cb1e8443%0A+Document+last+modified%3A+2025-11-16T23%3A18%3A00.000Z%0A%0A%3C%2Fdetails%3E "This will take you to GitHub to file a new issue.") 1. [HTTP](https://developer.mozilla.org/en-US/docs/Web/HTTP) 2. [Guides](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides) 3. [Overview of HTTP](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Overview) 4. [Evolution of HTTP](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Evolution_of_HTTP) 5. [A typical HTTP session](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Session) 6. [HTTP messages](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Messages) 7. [Media types](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/MIME_types) 1. [Common types](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/MIME_types/Common_types) 8. [Compression in HTTP](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Compression) 9. [HTTP caching](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching) 10. [HTTP authentication](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Authentication) 11. [Using HTTP cookies](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Cookies) 12. [Redirections in HTTP](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Redirections) 13. [Conditional requests](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Conditional_requests) 14. [Range requests](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Range_requests) 15. [Client hints](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Client_hints) 16. [User-Agent reduction](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/User-agent_reduction) 17. [Compression Dictionary Transport](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Compression_dictionary_transport) Experimental 18. [Network Error Logging](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Network_Error_Logging) Experimental 19. [Content negotiation](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Content_negotiation) 1. [Default Accept values](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Content_negotiation/List_of_default_Accept_values) 20. [Browser detection using the UA string](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Browser_detection_using_the_user_agent) 21. [Connection management in HTTP/1.x](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Connection_management_in_HTTP_1.x) 22. [Protocol upgrade mechanism](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Protocol_upgrade_mechanism) 23. [Proxy servers and tunneling](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Proxy_servers_and_tunneling) 1. [Proxy Auto-Configuration (PAC) file](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Proxy_servers_and_tunneling/Proxy_Auto-Configuration_PAC_file) 24. Security and privacy 1. [HTTP Observatory](https://developer.mozilla.org/en-US/observatory) 2. [Practical implementation guides](https://developer.mozilla.org/en-US/docs/Web/Security/Practical_implementation_guides) 3. [Permissions Policy](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Permissions_Policy) Experimental 4. [Cross-Origin Resource Policy (CORP)](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Cross-Origin_Resource_Policy) 5. [IFrame credentialless](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/IFrame_credentialless) Experimental 6. [Fetch metadata](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Fetch_metadata) 7. [Cross-Origin Resource Sharing (CORS)](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CORS) 8. [CORS errors](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CORS/Errors) 1. [`Reason: CORS disabled`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CORS/Errors/CORSDisabled) 2. [`Reason: CORS header 'Access-Control-Allow-Origin' does not match 'xyz'`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CORS/Errors/CORSAllowOriginNotMatchingOrigin) 3. [`Reason: CORS header 'Access-Control-Allow-Origin' missing`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CORS/Errors/CORSMissingAllowOrigin) 4. [`Reason: CORS header 'Origin' cannot be added`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CORS/Errors/CORSOriginHeaderNotAdded) 5. [`Reason: CORS preflight channel did not succeed`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CORS/Errors/CORSPreflightDidNotSucceed) 6. [`Reason: CORS request did not succeed`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CORS/Errors/CORSDidNotSucceed) 7. [`Reason: CORS request external redirect not allowed`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CORS/Errors/CORSExternalRedirectNotAllowed) 8. [`Reason: CORS request not HTTP`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CORS/Errors/CORSRequestNotHttp) 9. [`Reason: Credential is not supported if the CORS header 'Access-Control-Allow-Origin' is ''`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CORS/Errors/CORSNotSupportingCredentials) 10. [`Reason: Did not find method in CORS header 'Access-Control-Allow-Methods'`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CORS/Errors/CORSMethodNotFound) 11. [`Reason: expected 'true' in CORS header 'Access-Control-Allow-Credentials'`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CORS/Errors/CORSMIssingAllowCredentials) 12. [`Reason: invalid token 'xyz' in CORS header 'Access-Control-Allow-Headers'`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CORS/Errors/CORSInvalidAllowHeader) 13. [`Reason: invalid token 'xyz' in CORS header 'Access-Control-Allow-Methods'`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CORS/Errors/CORSInvalidAllowMethod) 14. [`Reason: missing token 'xyz' in CORS header 'Access-Control-Allow-Headers' from CORS preflight channel`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CORS/Errors/CORSMissingAllowHeaderFromPreflight) 15. [`Reason: Multiple CORS header 'Access-Control-Allow-Origin' not allowed`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CORS/Errors/CORSMultipleAllowOriginNotAllowed) 9. [Content Security Policy (CSP)](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CSP) 1. [Errors and warnings](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CSP/Errors) 25. [Reference](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference) 26. [HTTP headers](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers) 1. [`Accept`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Accept) 2. [`Accept-CH`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Accept-CH) 3. [`Accept-Encoding`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Accept-Encoding) 4. [`Accept-Language`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Accept-Language) 5. [`Accept-Patch`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Accept-Patch) 6. [`Accept-Post`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Accept-Post) 7. [`Accept-Ranges`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Accept-Ranges) 8. [`Access-Control-Allow-Credentials`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Access-Control-Allow-Credentials) 9. [`Access-Control-Allow-Headers`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Access-Control-Allow-Headers) 10. [`Access-Control-Allow-Methods`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Access-Control-Allow-Methods) 11. [`Access-Control-Allow-Origin`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Access-Control-Allow-Origin) 12. [`Access-Control-Expose-Headers`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Access-Control-Expose-Headers) 13. [`Access-Control-Max-Age`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Access-Control-Max-Age) 14. [`Access-Control-Request-Headers`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Access-Control-Request-Headers) 15. [`Access-Control-Request-Method`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Access-Control-Request-Method) 16. [`Activate-Storage-Access`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Activate-Storage-Access) 17. [`Age`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Age) 18. [`Allow`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Allow) 19. [`Alt-Svc`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Alt-Svc) 20. [`Alt-Used`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Alt-Used) 21. [`Attribution-Reporting-Eligible`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Attribution-Reporting-Eligible) Deprecated 22. [`Attribution-Reporting-Register-Source`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Attribution-Reporting-Register-Source) Deprecated 23. [`Attribution-Reporting-Register-Trigger`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Attribution-Reporting-Register-Trigger) Deprecated 24. [`Authorization`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Authorization) 25. [`Available-Dictionary`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Available-Dictionary) Experimental 26. [`Cache-Control`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control) 27. [`Clear-Site-Data`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Clear-Site-Data) 28. [`Connection`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Connection) 29. [`Content-Digest`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Digest) 30. [`Content-Disposition`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Disposition) 31. [`Content-DPR`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-DPR) Non-standard Deprecated 32. [`Content-Encoding`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Encoding) 33. [`Content-Language`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Language) 34. [`Content-Length`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Length) 35. [`Content-Location`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Location) 36. [`Content-Range`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Range) 37. [`Content-Security-Policy`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy) 38. [`Content-Security-Policy-Report-Only`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy-Report-Only) 39. [`Content-Type`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Type) 40. [`Cookie`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cookie) 41. [`Critical-CH`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Critical-CH) Experimental 42. [`Cross-Origin-Embedder-Policy`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cross-Origin-Embedder-Policy) 43. [`Cross-Origin-Embedder-Policy-Report-Only`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cross-Origin-Embedder-Policy-Report-Only) 44. [`Cross-Origin-Opener-Policy`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cross-Origin-Opener-Policy) 45. [`Cross-Origin-Resource-Policy`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cross-Origin-Resource-Policy) 46. [`Date`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Date) 47. [`Device-Memory`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Device-Memory) Non-standard Deprecated 48. [`Dictionary-ID`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Dictionary-ID) Experimental 49. [`DNT`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/DNT) Non-standard Deprecated 50. [`Downlink`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Downlink) Experimental 51. [`DPR`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/DPR) Non-standard Deprecated 52. [`Early-Data`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Early-Data) Experimental 53. [`ECT`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/ECT) Experimental 54. [`ETag`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/ETag) 55. [`Expect`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Expect) 56. [`Expect-CT`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Expect-CT) Deprecated 57. [`Expires`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Expires) 58. [`Forwarded`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Forwarded) 59. [`From`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/From) 60. [`Host`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Host) 61. [`Idempotency-Key`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Idempotency-Key) Experimental 62. [`If-Match`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/If-Match) 63. [`If-Modified-Since`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/If-Modified-Since) 64. [`If-None-Match`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/If-None-Match) 65. [`If-Range`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/If-Range) 66. [`If-Unmodified-Since`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/If-Unmodified-Since) 67. [`Integrity-Policy`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Integrity-Policy) 68. [`Integrity-Policy-Report-Only`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Integrity-Policy-Report-Only) 69. [`Keep-Alive`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Keep-Alive) 70. [`Last-Modified`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Last-Modified) 71. [`Link`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Link) 72. [`Location`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Location) 73. [`Max-Forwards`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Max-Forwards) 74. [`NEL`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/NEL) Experimental 75. [`No-Vary-Search`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/No-Vary-Search) Experimental 76. [`Observe-Browsing-Topics`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Observe-Browsing-Topics) Non-standard Deprecated 77. [`Origin`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Origin) 78. [`Origin-Agent-Cluster`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Origin-Agent-Cluster) 79. [`Permissions-Policy`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy) Experimental 80. [`Pragma`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Pragma) Deprecated 81. [`Prefer`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Prefer) 82. [`Preference-Applied`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Preference-Applied) 83. [`Priority`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Priority) 84. [`Proxy-Authenticate`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Proxy-Authenticate) 85. [`Proxy-Authorization`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Proxy-Authorization) 86. [`Range`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Range) 87. [`Referer`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Referer) 88. [`Referrer-Policy`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Referrer-Policy) 89. [`Refresh`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Refresh) 90. [`Report-To`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Report-To) Non-standard Deprecated 91. [`Reporting-Endpoints`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Reporting-Endpoints) 92. [`Repr-Digest`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Repr-Digest) 93. [`Retry-After`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Retry-After) 94. [`RTT`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/RTT) Experimental 95. [`Save-Data`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Save-Data) Experimental 96. [`Sec-Browsing-Topics`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-Browsing-Topics) Non-standard Deprecated 97. [`Sec-CH-Device-Memory`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-CH-Device-Memory) Experimental 98. [`Sec-CH-DPR`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-CH-DPR) Experimental 99. [`Sec-CH-Prefers-Color-Scheme`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-CH-Prefers-Color-Scheme) Experimental 100. [`Sec-CH-Prefers-Reduced-Motion`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-CH-Prefers-Reduced-Motion) Experimental 101. [`Sec-CH-Prefers-Reduced-Transparency`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-CH-Prefers-Reduced-Transparency) Experimental 102. [`Sec-CH-UA`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-CH-UA) Experimental 103. [`Sec-CH-UA-Arch`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-CH-UA-Arch) Experimental 104. [`Sec-CH-UA-Bitness`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-CH-UA-Bitness) Experimental 105. [`Sec-CH-UA-Form-Factors`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-CH-UA-Form-Factors) Experimental 106. [`Sec-CH-UA-Full-Version`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-CH-UA-Full-Version) Deprecated 107. [`Sec-CH-UA-Full-Version-List`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-CH-UA-Full-Version-List) Experimental 108. [`Sec-CH-UA-Mobile`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-CH-UA-Mobile) Experimental 109. [`Sec-CH-UA-Model`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-CH-UA-Model) Experimental 110. [`Sec-CH-UA-Platform`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-CH-UA-Platform) Experimental 111. [`Sec-CH-UA-Platform-Version`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-CH-UA-Platform-Version) Experimental 112. [`Sec-CH-UA-WoW64`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-CH-UA-WoW64) Experimental 113. [`Sec-CH-Viewport-Height`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-CH-Viewport-Height) Experimental 114. [`Sec-CH-Viewport-Width`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-CH-Viewport-Width) Experimental 115. [`Sec-CH-Width`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-CH-Width) Experimental 116. [`Sec-Fetch-Dest`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-Fetch-Dest) 117. [`Sec-Fetch-Mode`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-Fetch-Mode) 118. [`Sec-Fetch-Site`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-Fetch-Site) 119. [`Sec-Fetch-Storage-Access`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-Fetch-Storage-Access) 120. [`Sec-Fetch-User`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-Fetch-User) 121. [`Sec-GPC`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-GPC) Experimental 122. [`Sec-Private-State-Token`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-Private-State-Token) Experimental 123. [`Sec-Private-State-Token-Crypto-Version`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-Private-State-Token-Crypto-Version) Experimental 124. [`Sec-Private-State-Token-Lifetime`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-Private-State-Token-Lifetime) Experimental 125. [`Sec-Purpose`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-Purpose) 126. [`Sec-Redemption-Record`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-Redemption-Record) Experimental 127. [`Sec-Speculation-Tags`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-Speculation-Tags) Experimental 128. [`Sec-WebSocket-Accept`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-WebSocket-Accept) 129. [`Sec-WebSocket-Extensions`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-WebSocket-Extensions) 130. [`Sec-WebSocket-Key`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-WebSocket-Key) 131. [`Sec-WebSocket-Protocol`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-WebSocket-Protocol) 132. [`Sec-WebSocket-Version`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-WebSocket-Version) 133. [`Server`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Server) 134. [`Server-Timing`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Server-Timing) 135. [`Service-Worker`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Service-Worker) 136. [`Service-Worker-Allowed`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Service-Worker-Allowed) 137. [`Service-Worker-Navigation-Preload`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Service-Worker-Navigation-Preload) 138. [`Set-Cookie`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Set-Cookie) 139. [`Set-Login`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Set-Login) 140. [`SourceMap`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/SourceMap) 141. [`Speculation-Rules`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Speculation-Rules) Experimental 142. [`Strict-Transport-Security`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Strict-Transport-Security) 143. [`Supports-Loading-Mode`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Supports-Loading-Mode) Experimental 144. [`TE`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/TE) 145. [`Timing-Allow-Origin`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Timing-Allow-Origin) 146. [`Tk`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Tk) Non-standard Deprecated 147. [`Trailer`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Trailer) 148. [`Transfer-Encoding`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Transfer-Encoding) 149. [`Upgrade`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Upgrade) 150. [`Upgrade-Insecure-Requests`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Upgrade-Insecure-Requests) 151. [`Use-As-Dictionary`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Use-As-Dictionary) Experimental 152. [`User-Agent`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/User-Agent) 153. [`Vary`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Vary) 154. [`Via`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Via) 155. [`Viewport-Width`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Viewport-Width) Non-standard Deprecated 156. [`Want-Content-Digest`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Want-Content-Digest) 157. [`Want-Repr-Digest`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Want-Repr-Digest) 158. [`Warning`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Warning) Deprecated 159. [`Width`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Width) Non-standard Deprecated 160. [`WWW-Authenticate`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/WWW-Authenticate) 161. [`X-Content-Type-Options`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/X-Content-Type-Options) 162. [`X-DNS-Prefetch-Control`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/X-DNS-Prefetch-Control) Non-standard 163. [`X-Forwarded-For`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/X-Forwarded-For) Non-standard 164. [`X-Forwarded-Host`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/X-Forwarded-Host) Non-standard 165. [`X-Forwarded-Proto`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/X-Forwarded-Proto) Non-standard 166. [`X-Frame-Options`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/X-Frame-Options) 167. [`X-Permitted-Cross-Domain-Policies`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/X-Permitted-Cross-Domain-Policies) Non-standard 168. [`X-Powered-By`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/X-Powered-By) Non-standard 169. [`X-Robots-Tag`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/X-Robots-Tag) Non-standard 170. [`X-XSS-Protection`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/X-XSS-Protection) Non-standard Deprecated 27. [HTTP request methods](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Methods) 1. [`CONNECT`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Methods/CONNECT) 2. [`DELETE`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Methods/DELETE) 3. [`GET`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Methods/GET) 4. [`HEAD`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Methods/HEAD) 5. [`OPTIONS`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Methods/OPTIONS) 6. [`PATCH`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Methods/PATCH) 7. [`POST`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Methods/POST) 8. [`PUT`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Methods/PUT) 9. [`TRACE`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Methods/TRACE) 28. [HTTP response status codes](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status) 1. [`100 Continue`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/100) 2. [`101 Switching Protocols`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/101) 3. [`102 Processing`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/102) 4. [`103 Early Hints`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/103) 5. [`200 OK`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/200) 6. [`201 Created`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/201) 7. [`202 Accepted`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/202) 8. [`203 Non-Authoritative Information`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/203) 9. [`204 No Content`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/204) 10. [`205 Reset Content`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/205) 11. [`206 Partial Content`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/206) 12. [`207 Multi-Status`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/207) 13. [`208 Already Reported`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/208) 14. [`226 IM Used`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/226) 15. [`300 Multiple Choices`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/300) 16. [`301 Moved Permanently`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/301) 17. [`302 Found`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/302) 18. [`303 See Other`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/303) 19. [`304 Not Modified`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/304) 20. [`307 Temporary Redirect`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/307) 21. [`308 Permanent Redirect`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/308) 22. [`400 Bad Request`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/400) 23. [`401 Unauthorized`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/401) 24. [`402 Payment Required`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/402) 25. [`403 Forbidden`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/403) 26. [`404 Not Found`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/404) 27. [`405 Method Not Allowed`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/405) 28. [`406 Not Acceptable`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/406) 29. [`407 Proxy Authentication Required`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/407) 30. [`408 Request Timeout`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/408) 31. [`409 Conflict`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/409) 32. [`410 Gone`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/410) 33. [`411 Length Required`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/411) 34. [`412 Precondition Failed`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/412) 35. [`413 Content Too Large`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/413) 36. [`414 URI Too Long`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/414) 37. [`415 Unsupported Media Type`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/415) 38. [`416 Range Not Satisfiable`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/416) 39. [`417 Expectation Failed`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/417) 40. [`418 I'm a teapot`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/418) 41. [`421 Misdirected Request`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/421) 42. [`422 Unprocessable Content`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/422) 43. [`423 Locked`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/423) 44. [`424 Failed Dependency`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/424) 45. [`425 Too Early`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/425) 46. [`426 Upgrade Required`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/426) 47. [`428 Precondition Required`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/428) 48. [`429 Too Many Requests`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/429) 49. [`431 Request Header Fields Too Large`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/431) 50. [`451 Unavailable For Legal Reasons`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/451) 51. [`500 Internal Server Error`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/500) 52. [`501 Not Implemented`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/501) 53. [`502 Bad Gateway`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/502) 54. [`503 Service Unavailable`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/503) 55. [`504 Gateway Timeout`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/504) 56. [`505 HTTP Version Not Supported`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/505) 57. [`506 Variant Also Negotiates`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/506) 58. [`507 Insufficient Storage`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/507) 59. [`508 Loop Detected`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/508) 60. [`510 Not Extended`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/510) 61. [`511 Network Authentication Required`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/511) 29. [CSP directives](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy#directives) 1. [`base-uri`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/base-uri) 2. [`block-all-mixed-content`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/block-all-mixed-content) Deprecated 3. [`child-src`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/child-src) 4. [`connect-src`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/connect-src) 5. [`default-src`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/default-src) 6. [`fenced-frame-src`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/fenced-frame-src) Experimental 7. [`font-src`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/font-src) 8. [`form-action`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/form-action) 9. [`frame-ancestors`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/frame-ancestors) 10. [`frame-src`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/frame-src) 11. [`img-src`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/img-src) 12. [`manifest-src`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/manifest-src) 13. [`media-src`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/media-src) 14. [`object-src`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/object-src) 15. [`prefetch-src`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/prefetch-src) Non-standard Deprecated 16. [`report-to`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/report-to) 17. [`report-uri`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/report-uri) Deprecated 18. [`require-trusted-types-for`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/require-trusted-types-for) 19. [`sandbox`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/sandbox) 20. [`script-src`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/script-src) 21. [`script-src-attr`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/script-src-attr) 22. [`script-src-elem`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/script-src-elem) 23. [`style-src`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/style-src) 24. [`style-src-attr`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/style-src-attr) 25. [`style-src-elem`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/style-src-elem) 26. [`trusted-types`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/trusted-types) 27. [`upgrade-insecure-requests`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/upgrade-insecure-requests) 28. [`worker-src`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Security-Policy/worker-src) 30. [Permissions-Policy directives](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy#directives) Experimental 1. [`accelerometer`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/accelerometer) Experimental 2. [`ambient-light-sensor`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/ambient-light-sensor) Experimental 3. [`aria-notify`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/aria-notify) Experimental 4. [`attribution-reporting`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/attribution-reporting) Deprecated 5. [`autoplay`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/autoplay) Experimental 6. [`bluetooth`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/bluetooth) Experimental 7. [`browsing-topics`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/browsing-topics) Non-standard Deprecated 8. [`camera`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/camera) Experimental 9. [`captured-surface-control`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/captured-surface-control) Experimental 10. [`ch-ua-high-entropy-values`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/ch-ua-high-entropy-values) Experimental 11. [`compute-pressure`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/compute-pressure) Experimental 12. [`cross-origin-isolated`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/cross-origin-isolated) Experimental 13. [`deferred-fetch`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/deferred-fetch) Experimental 14. [`deferred-fetch-minimal`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/deferred-fetch-minimal) Experimental 15. [`display-capture`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/display-capture) Experimental 16. [`encrypted-media`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/encrypted-media) Experimental 17. [`fullscreen`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/fullscreen) Experimental 18. [`gamepad`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/gamepad) Experimental 19. [`geolocation`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/geolocation) Experimental 20. [`gyroscope`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/gyroscope) Experimental 21. [`hid`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/hid) Experimental 22. [`identity-credentials-get`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/identity-credentials-get) Experimental 23. [`idle-detection`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/idle-detection) Experimental 24. [`language-detector`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/language-detector) Experimental 25. [`local-fonts`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/local-fonts) Experimental 26. [`magnetometer`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/magnetometer) Experimental 27. [`microphone`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/microphone) Experimental 28. [`midi`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/midi) Experimental 29. [`on-device-speech-recognition`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/on-device-speech-recognition) Experimental 30. [`otp-credentials`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/otp-credentials) Experimental 31. [`payment`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/payment) Experimental 32. [`picture-in-picture`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/picture-in-picture) Experimental 33. [`private-state-token-issuance`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/private-state-token-issuance) Experimental 34. [`private-state-token-redemption`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/private-state-token-redemption) Experimental 35. [`publickey-credentials-create`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/publickey-credentials-create) Experimental 36. [`publickey-credentials-get`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/publickey-credentials-get) Experimental 37. [`screen-wake-lock`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/screen-wake-lock) Experimental 38. [`serial`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/serial) Experimental 39. [`speaker-selection`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/speaker-selection) Experimental 40. [`storage-access`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/storage-access) Experimental 41. [`summarizer`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/summarizer) Experimental 42. [`translator`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/translator) Experimental 43. [`usb`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/usb) Experimental 44. [`web-share`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/web-share) Experimental 45. [`window-management`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/window-management) Experimental 46. [`xr-spatial-tracking`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy/xr-spatial-tracking) Experimental 31. [HTTP resources and specifications](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Resources_and_specifications) Your blueprint for a better internet. 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Readable Markdown	## [Syntax](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#syntax) http ``` Cache-Control: <directive>, <directive>, ... ``` Cache directives follow these rules: - Caching directives are case-insensitive. However, lowercase is recommended because some implementations do not recognize uppercase directives. - Multiple directives are permitted and must be comma-separated (e.g., `Cache-control: max-age=180, public`). - Some directives have an optional argument. When an argument is provided, it is separated from the directive name by an equals symbol (`=`). Typically, arguments for the directives are integers and are therefore not enclosed in quote characters (e.g., `Cache-control: max-age=12`). ### [Cache directives](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#cache_directives) The following table lists the standard `Cache-Control` directives: \| Request \| Response \| \|---\|---\| \| `max-age` \| `max-age` \| \| `max-stale` \| \- \| \| `min-fresh` \| \- \| \| \- \| `s-maxage` \| \| `no-cache` \| `no-cache` \| \| `no-store` \| `no-store` \| \| `no-transform` \| `no-transform` \| \| `only-if-cached` \| \- \| \| \- \| `must-revalidate` \| \| \- \| `proxy-revalidate` \| \| \- \| `must-understand` \| \| \- \| `private` \| \| \- \| `public` \| \| \- \| `immutable` \| \| \- \| `stale-while-revalidate` \| \| `stale-if-error` \| `stale-if-error` \| Note: Check the [compatibility table](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#browser_compatibility) for their support; user agents that don't recognize them should ignore them. ## [Vocabulary](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#vocabulary) This section defines the terms used in this document, some of which are from the specification. [(HTTP) cache](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#http_cache) Implementation that holds requests and responses for reusing in subsequent requests. It can be either a shared cache or a private cache. [Shared cache](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#shared_cache) Cache that exists between the origin server and clients (e.g., Proxy, CDN). It stores a single response and reuses it with multiple users — so developers should avoid storing personalized contents to be cached in the shared cache. [Private cache](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#private_cache) Cache that exists in the client. It is also called local cache or browser cache. It can store and reuse personalized content for a single user. [Store response](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#store_response) Store a response in caches when the response is cacheable. However, the cached response is not always reused as-is. (Usually, "cache" means storing a response.) [Reuse response](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#reuse_response) Reuse cached responses for subsequent requests. [Revalidate response](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#revalidate_response) Ask the origin server whether or not the stored response is still [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age). Usually, the revalidation is done through a conditional request. [Fresh response](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#fresh_response) Indicates that the response is [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age). This usually means the response can be reused for subsequent requests, depending on request directives. [Stale response](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#stale_response) Indicates that the response is a [stale response](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age). This usually means the response can't be reused as-is. Cache storage isn't required to remove stale responses immediately because revalidation could change the response from being stale to being [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) again. [Age](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#age) The time since a response was generated. It is a criterion for whether a response is [fresh or stale](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age). ## [Directives](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#directives) This section lists directives that affect caching — both response directives and request directives. ### [Response Directives](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#response_directives) #### `max-age` The `max-age=N` response directive indicates that the response remains [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) until N seconds after the response is generated. http ``` Cache-Control: max-age=604800 ``` Indicates that caches can store this response and reuse it for subsequent requests while it's [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age). Note that `max-age` is not the elapsed time since the response was received; it is the elapsed time since the response was generated on the origin server. So if the other cache(s) — on the network route taken by the response — store the response for 100 seconds (indicated using the `Age` response header field), the browser cache would deduct 100 seconds from its [freshness lifetime](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age). If the `max-age` value is negative (for example, `-1`) or isn't an integer (for example, `3599.99`), then the caching behavior is unspecified. Caches are encouraged to treat the value as if it were `0` (this is noted in the [Calculating Freshness Lifetime](https://httpwg.org/specs/rfc9111.html#calculating.freshness.lifetime) section of the HTTP specification). http ``` Cache-Control: max-age=604800 Age: 100 ``` #### `s-maxage` The `s-maxage` response directive indicates how long the response remains [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) in a shared cache. The `s-maxage` directive is ignored by private caches, and overrides the value specified by the `max-age` directive or the `Expires` header for shared caches, if they are present. http ``` Cache-Control: s-maxage=604800 ``` #### `no-cache` The `no-cache` response directive indicates that the response can be stored in caches, but the response must be validated with the origin server before each reuse, even when the cache is disconnected from the origin server. http ``` Cache-Control: no-cache ``` If you want caches to always check for content updates while reusing stored content, `no-cache` is the directive to use. It does this by requiring caches to revalidate each request with the origin server. Note that `no-cache` does not mean "don't cache". `no-cache` allows caches to store a response but requires them to revalidate it before reuse. If the sense of "don't cache" that you want is actually "don't store", then `no-store` is the directive to use. #### `must-revalidate` The `must-revalidate` response directive indicates that the response can be stored in caches and can be reused while [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age). If the response becomes [stale](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age), it must be validated with the origin server before reuse. Typically, `must-revalidate` is used with `max-age`. http ``` Cache-Control: max-age=604800, must-revalidate ``` HTTP allows caches to reuse [stale responses](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) when they are disconnected from the origin server. `must-revalidate` is a way to prevent this from happening - either the stored response is revalidated with the origin server or a 504 (Gateway Timeout) response is generated. #### `proxy-revalidate` The `proxy-revalidate` response directive is the equivalent of `must-revalidate`, but specifically for shared caches only. #### `no-store` The `no-store` response directive indicates that any caches of any kind (private or shared) should not store this response. http ``` Cache-Control: no-store ``` #### `private` The `private` response directive indicates that the response can be stored only in a private cache (e.g., local caches in browsers). http ``` Cache-Control: private ``` You should add the `private` directive for user-personalized content, especially for responses received after login and for sessions managed via cookies. If you forget to add `private` to a response with personalized content, then that response can be stored in a shared cache and end up being reused for multiple users, which can cause personal information to leak. #### `public` The `public` response directive indicates that the response can be stored in a shared cache. Responses for requests with `Authorization` header fields must not be stored in a shared cache; however, the `public` directive will cause such responses to be stored in a shared cache. http ``` Cache-Control: public ``` In general, when pages are under Basic Auth or Digest Auth, the browser sends requests with the `Authorization` header. This means that the response is access-controlled for restricted users (who have accounts), and it's fundamentally not shared-cacheable, even if it has `max-age`. You can use the `public` directive to unlock that restriction. http ``` Cache-Control: public, max-age=604800 ``` Note that `s-maxage` or `must-revalidate` also unlock that restriction. If a request doesn't have an `Authorization` header, or you are already using `s-maxage` or `must-revalidate` in the response, then you don't need to use `public`. #### `must-understand` The `must-understand` response directive indicates that a cache should store the response only if it understands the requirements for caching based on status code. `must-understand` should be coupled with `no-store` for fallback behavior. http ``` Cache-Control: must-understand, no-store ``` If a cache doesn't support `must-understand`, it will be ignored. If `no-store` is also present, the response isn't stored. If a cache supports `must-understand`, it stores the response with an understanding of cache requirements based on its status code. #### `no-transform` Some intermediaries transform content for various reasons. For example, some convert images to reduce transfer size. In some cases, this is undesirable for the content provider. `no-transform` indicates that any intermediary (regardless of whether it implements a cache) shouldn't transform the response contents. #### `immutable` The `immutable` response directive indicates that the response will not be updated while it's [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age). http ``` Cache-Control: public, max-age=604800, immutable ``` A modern best practice for static resources is to include version/hashes in their URLs, while never modifying the resources — but instead, when necessary, updating the resources with newer versions that have new version-numbers/hashes, so that their URLs are different. That's called the cache-busting pattern. html ``` <script src="https://example.com/react.0.0.0.js"></script> ``` When a user reloads the browser, the browser will send conditional requests for validating to the origin server. But it's not necessary to revalidate those kinds of static resources even when a user reloads the browser, because they're never modified. `immutable` tells a cache that the response is immutable while it's [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) and avoids those kinds of unnecessary conditional requests to the server. When you use a cache-busting pattern for resources and apply them to a long `max-age`, you can also add `immutable` to avoid revalidation. #### `stale-while-revalidate` The `stale-while-revalidate` response directive indicates that the cache could reuse a stale response while it revalidates it to a cache. http ``` Cache-Control: max-age=604800, stale-while-revalidate=86400 ``` In the example above, the response is [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) for 7 days (604800s). After 7 days it becomes [stale](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age), but the cache is allowed to reuse it for any requests that are made in the following day (86400s), provided that they revalidate the response in the background. Revalidation will make the cache be [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) again, so it appears to clients that it was always [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) during that period — effectively hiding the latency penalty of revalidation from them. If no request happened during that period, the cache became [stale](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) and the next request will revalidate normally. #### `stale-if-error` The `stale-if-error` response directive indicates that the cache can reuse a [stale response](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) when an upstream server generates an error, or when the error is generated locally. Here, an error is considered any response with a status code of 500, 502, 503, or 504. http ``` Cache-Control: max-age=604800, stale-if-error=86400 ``` In the example above, the response is [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) for 7 days (604800s). Afterwards, it becomes [stale](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age), but can be used for an extra 1 day (86400s) when an error is encountered. After the stale-if-error period passes, the client will receive any error generated. ### [Request Directives](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#request_directives) #### `no-cache` The `no-cache` request directive asks caches to validate the response with the origin server before reuse. http ``` Cache-Control: no-cache ``` `no-cache` allows clients to request the most up-to-date response even if the cache has a [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) response. Browsers usually add `no-cache` to requests when users are force reloading a page. #### `no-store` The `no-store` request directive allows a client to request that caches refrain from storing the request and corresponding response — even if the origin server's response could be stored. http ``` Cache-Control: no-store ``` #### `max-age` The `max-age=N` request directive indicates that the client allows a stored response that is generated on the origin server within N seconds — where N may be any non-negative integer (including `0`). http ``` Cache-Control: max-age=10800 ``` In the case above, if the response with `Cache-Control: max-age=10800` was generated more than 3 hours ago (calculated from `max-age` and the `Age` header), the cache couldn't reuse that response. Many browsers use this directive for reloading, as explained below. http ``` Cache-Control: max-age=0 ``` `max-age=0` is a workaround for `no-cache`, because many old (HTTP/1.0) cache implementations don't support `no-cache`. Recently browsers are still using `max-age=0` in "reloading" — for backward compatibility — and alternatively using `no-cache` to cause a "force reloading". If the `max-age` value is negative (for example, `-1`) or isn't an integer (for example, `3599.99`), then the caching behavior is unspecified. Caches are encouraged to treat the value as if it were `0`. #### `max-stale` The `max-stale=N` request directive indicates that the client allows a stored response that is [stale](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) within N seconds. If no N value is specified, the client will accept a stale response of any age. http ``` Cache-Control: max-stale=3600 ``` For example, a request with the header above indicates that the browser will accept a stale response from the cache that has expired within the last hour. Clients can use this header when the origin server is down or too slow and can accept cached responses from caches even if they are a bit old. Note that the major browsers do not support requests with `max-stale`. #### `min-fresh` The `min-fresh=N` request directive indicates that the client allows a stored response that is [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) for at least N seconds. http ``` Cache-Control: min-fresh=600 ``` In the case above, if the response with `Cache-Control: max-age=3600` was stored in caches 51 minutes ago, the cache couldn't reuse that response. Clients can use this header when the user requires the response to not only be [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age), but also requires that it won't be updated for a period of time. Note that the major browsers do not support requests with `min-fresh`. #### `no-transform` Same meaning that `no-transform` has for a response, but for a request instead. #### `only-if-cached` The client indicates that an already-cached response should be returned. If a cache has a stored response, even a stale one, it will be returned. If no cached response is available, a [504 Gateway Timeout](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/504) response will be returned. #### `stale-if-error` The `stale-if-error` request directive indicates that the browser is interested in receiving stale content on error from any intermediate server for a particular origin. This is not supported by any browser (see [Browser compatibility](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#browser_compatibility)). ## [Use Cases](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#use_cases) ### [Preventing storing](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#preventing_storing) If you don't want a response stored in caches, use the `no-store` directive. http ``` Cache-Control: no-store ``` Note that `no-cache` means "it can be stored but don't reuse before validating" — so it's not for preventing a response from being stored. http ``` Cache-Control: no-cache ``` In theory, if directives are conflicted, the most restrictive directive should be honored. So the example below is basically meaningless because `private`, `no-cache`, `max-age=0` and `must-revalidate` conflict with `no-store`. http ``` # conflicted Cache-Control: private, no-cache, no-store, max-age=0, must-revalidate # equivalent to Cache-Control: no-store ``` ### [Caching static assets with "cache busting"](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#caching_static_assets_with_cache_busting) When you build static assets with versioning/hashing mechanisms, adding a version/hash to the filename or query string is a good way to manage caching. For example: html ``` <!-- index.html --> <script src="/assets/react.min.js"></script> <img src="/assets/hero.png" width="900" height="400" /> ``` The React library version will change when you update the library, and `hero.png` will also change when you edit the picture. So those are hard to store in a cache with `max-age`. In such a case, you could address the caching needs by using a specific, numbered version of the library, and including the hash of the picture in its URL. html ``` <!-- index.html --> <script src="/assets/react.0.0.0min.js"></script> <img src="/assets/hero.png?hash=deadbeef" width="900" height="400" /> ``` You can add a long `max-age` value and `immutable` because the content will never change. http ``` # /assets/* Cache-Control: max-age=31536000, immutable ``` When you update the library or edit the picture, new content should have a new URL, and caches aren't reused. That is called the "cache busting" pattern. Use a `no-cache` to make sure that the HTML response itself is not cached. `no-cache` could cause revalidation, and the client will correctly receive a new version of the HTML response and static assets. http ``` # /index.html Cache-Control: no-cache ``` Note: If `index.html` is controlled under Basic Authentication or Digest Authentication, files under `/assets` are not stored in the shared cache. If `/assets/` files are suitable for storing in a shared cache, you also need one of `public`, `s-maxage` or `must-revalidate`. ### [Up-to-date contents always](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#up-to-date_contents_always) For content that's generated dynamically, or that's static but updated often, you want a user to always receive the most up-to-date version. If you don't add a `Cache-Control` header because the response is not intended to be cached, that could cause an unexpected result. Cache storage is allowed to cache it heuristically — so if you have any requirements on caching, you should always indicate them explicitly, in the `Cache-Control` header. Adding `no-cache` to the response causes revalidation to the server, so you can serve a [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) response every time — or if the client already has a new one, just respond `304 Not Modified`. http ``` Cache-Control: no-cache ``` Most HTTP/1.0 caches don't support `no-cache` directives, so historically `max-age=0` was used as a workaround. But only `max-age=0` could cause a [stale response](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) to be reused when caches disconnected from the origin server. `must-revalidate` addresses that. That's why the example below is equivalent to `no-cache`. http ``` Cache-Control: max-age=0, must-revalidate ``` But for now, you can simply use `no-cache` instead. ### [Clearing an already-stored cache](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#clearing_an_already-stored_cache) There are no cache directives for clearing already-stored responses from caches on intermediate servers. Imagine that clients/caches store a [fresh](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#fresh_and_stale_based_on_age) response for a path, with no request flight to the server. There is nothing a server could do to that path. [`Clear-Site-Data: cache`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Clear-Site-Data#cache) can be used to clear every stored response for a site in the browser cache, so use this with care. Note that this will not affect shared or intermediate caches. ## [Specifications](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#specifications) \| Specification \| \|---\| \| [HTTP Caching \# field.cache-control](https://httpwg.org/specs/rfc9111.html#field.cache-control) \| \| [HTTP Immutable Responses \# the-immutable-cache-control-extension](https://httpwg.org/specs/rfc8246.html#the-immutable-cache-control-extension) \| ## [Browser compatibility](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#browser_compatibility) ## [See also](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control#see_also) - [HTTP caching](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching) - [Caching Tutorial for Web Authors and Webmasters](https://www.mnot.net/cache_docs/) - [Caching best practices & max-age gotchas](https://jakearchibald.com/2016/caching-best-practices/) - [Cache-Control for Civilians](https://csswizardry.com/2019/03/cache-control-for-civilians/) - [RFC 9111 – HTTP Caching](https://httpwg.org/specs/rfc9111.html) - [RFC 5861 – HTTP Cache-Control Extensions for Stale Content](https://httpwg.org/specs/rfc5861.html) - [RFC 8246 – HTTP Immutable Responses](https://httpwg.org/specs/rfc8246.html)
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