The list is just examples of different techniques, it’s not for directinsertion. If copied, the second would overwrite the first and thefourth would overwrite the third because of the http-equivdeclarations AND fail with the W3C validator. At most, one could haveone of each http-equiv declarations; pragma, cache-control andexpires. These are completely outdated when using modern up to date browsers.After IE9 anyway. Chrome and Firefox specifically does not work with these as you would expect, if at all.
For modern web browsers (After IE
This page was last modified on Jul 4, 2025 by MDN contributors. Must-understand should be coupled with no-store for fallback behavior. You can use the public directive to unlock that restriction.
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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. This usually means the response can be reused for subsequent requests, depending on request directives. 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. The no-cache request directive asks caches to validate the response with the origin server before reuse.
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- In some cases, this is undesirable for the content provider.
- If no request happened during that period, the cache became stale and the next request will revalidate normally.
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. If you don’t want a response stored in caches, use the no-store directive. 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. Browsers usually add no-cache to requests when users are force reloading a page. No-cache allows clients to request the most up-to-date response even if the cache has a fresh response. 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.
immutable
- Alright, this is due to the pain that godaddy gives me by implementing their own caching in a MANAGED WORDPRESS hosting.
- No-cache could cause revalidation, and the client will correctly receive a new version of the HTML response and static assets.
- The immutable response directive indicates that the response will not be updated while it’s fresh.
- You can use the public directive to unlock that restriction.
- You should always use a real HTTP header for headers such as Cache-Control and Pragma.
- If a cache supports must-understand, it stores the response with an understanding of cache requirements based on its status code.
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. Note that the major browsers do not support requests with max-stale. Also, there is no setting to enable « development mode » which apparently turns off caching on the godaddy control panel. Caching headers are unreliable in meta elements; for one,any web proxies between the site and the user will completely ignorethem. You should always use a real HTTP header for headers such asCache-Control and Pragma. Note that the major browsers do not support requests with min-fresh.
Imagine that what is alphacon clients/caches store a fresh response for a path, with no request flight to the server. 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. 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. 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.
Middleware to turn off caching
No-transform indicates that any intermediary (regardless of whether it implements a cache) shouldn’t transform the response contents. If a cache doesn’t support must-understand, it will be ignored. Note that s-maxage or must-revalidate also unlock that restriction. When you open a translated website, you can switch between the original and translated versions. You can translate text, handwriting, photos, and speech in over 200 languages with the Google Translate app.
If a cache supports must-understand, it stores the response with an understanding of cache requirements based on its status code. This section lists directives that affect caching — both response directives and request directives. This Express middleware sets some HTTP response headers to try to disable client-side caching.
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. 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. 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.
To translate text, speech, and websites in more than 200 languages, go to Google Translate page. By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy. Alright, this is due to the pain that godaddy gives me by implementing their own caching in a MANAGED WORDPRESS hosting. I looked it up and as it turns out, their flush caching facility is not available to me in the wordpress dashboard as it is a subdirectory /wp/ installation.
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. The stale-while-revalidate response directive indicates that the cache could reuse a stale response while it revalidates it to a cache. The proxy-revalidate response directive is the equivalent of must-revalidate, but specifically for shared caches only. 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.
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. 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. The React library version will change when you update the library, and hero.png will also change when you edit the picture.
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. 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. The no-store response directive indicates that any caches of any kind (private or shared) should not store this response. Ask the origin server whether or not the stored response is still fresh. Usually, the revalidation is done through a conditional request. The Cache-Control header is used to specify directives for caching mechanisms in both HTTP requests and responses.
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. When you update the library or edit the picture, new content should have a new URL, and caches aren’t reused. 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.
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. 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. When a user reloads the browser, the browser will send conditional requests for validating to the origin server. Cache storage isn’t required to remove stale responses immediately because revalidation could change the response from being stale to being fresh again.