Cache-Control header HTTP MDN

No-cache could cause revalidation, and the client will correctly receive a new version of the HTML response and static assets. The React library version will change when you update the library, and hero.png will also change when you edit the picture. If you don’t want a response stored in caches, use the no-store directive. 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). 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.

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. There are no cache directives for clearing already-stored responses from caches on intermediate servers. When a user reloads the browser, the browser will send conditional requests for validating to the origin server. The client indicates that an already-cached response should be returned.

An explaination of the HTTP Cache-Control header

No-transform indicates that any intermediary (regardless of whether it implements a cache) shouldn’t transform the response contents. But you can’t invoke this option if the page isn’t or wasn’t already loaded. After entering this, your shell is a member of that cgroup, and any new processspawned will belong to that cgroup, too, and inherit the memory limit. Thecgroups created like this won’t be cleaned up automatically. This feature is well established and works across many devices and browser versions.

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. When you update the library or edit the picture, new content should have a new URL, and caches aren’t reused. 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.

Please note that nocache will only build on a system that hassupport for the posix_fadvise syscall and exposes it, too. Thisshould be the case on most modern Unices, but kfreebsd notably has nosupport for this as of now. However, cacheing headers are unreliable in meta elements; for one, any web proxies between the site and the user will completely ignore them. You should always use a real HTTP header for headers such as Cache-Control and Pragma. Note that the major browsers do not support requests with max-stale.

Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. However, since the actual fadvise calls are performed right beforethe file descriptor is closed, this may not happen if they are leftopen when the application exits, although the destructor tries to dothat. Caching headers are unreliable in meta elements; for one,any web proxies between the site and the user will completely ignorethem.

Skip-the-server-cache feature in browsers

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. 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 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.

How to run a process and its children in a memory-bounded cgroup

Note that the major browsers do not support requests with min-fresh. Many browsers use this directive for reloading, as explained below. After the stale-if-error period passes, the client will receive any error generated. If a cache doesn’t support must-understand, it will be ignored.

If no request happened during that period, the cache became stale and the next request will revalidate normally. 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 immutable response directive indicates that the response will not be updated while it’s fresh. Because the browser will update if and only if needed, there is no need to generally force a reload of all of the resources (the exception is if the data somehow gets corrupted, and then clearing the cache may solve the problem).

nocache – minimize filesystem caching effects

• If the sense of “don’t cache” that you want is actually “don’t store”, then no-store is the directive to use.
• If no request happened during that period, the cache became stale and the next request will revalidate normally.
• 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.
• 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.

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. This section lists directives that affect caching — both response directives and request directives. If you want to see this taking place (in not so much detail), open the developer panel in Chrome (using Ctrl+Shift+J), and reload a page. You will see that even for resources that were cached (under size, it will say from cache) there was a request for them.

• Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
• Thecgroups created like this won’t be cleaned up automatically.
• This feature is well established and works across many devices and browser versions.
• 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.
• This usually means the response can be reused for subsequent requests, depending on request directives.

The proxy-revalidate response directive is the equivalent of must-revalidate, but specifically for shared caches only. Cache storage isn’t required to remove stale responses immediately because revalidation could change the response from being stale to being fresh again. Imagine that clients/caches store a fresh response for a path, with no request flight to the server. 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. The stale-while-revalidate response directive indicates that the cache could reuse a stale response while it revalidates it to a cache. The no-store response directive indicates that any caches of any kind (private or shared) should not store this response.

For content that’s generated dynamically, or that’s static chicken road game download but updated often, you want a user to always receive the most up-to-date version. You can add a long max-age value and immutable because the content will never change. If a cache supports must-understand, it stores the response with an understanding of cache requirements based on its status code.

If the response becomes stale, it must be validated with the origin server before reuse. 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. 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. 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.

You should always use a real HTTP header for headers such asCache-Control and Pragma. 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.