Cache-Control HTTP Headers

Cache-Control HTTP Headers

HTTP 1.1에서는 헤더에 대한 새로운 컨트롤을 소개하고 있다. Cache-Control 응답 헤더가 그것인데, 이것은 웹 퍼블리셔에게 그들의 컨텐트를 더욱 많은 컨트롤을 제공하고, Expires의 제한에 대해서 말하고 있다.

유용한 Cache-Control응답 헤더 :

• max-age=[seconds] — specifies the maximum amount of time that an representation will be considered fresh. Similar to Expires, this directive is relative to the time of the request, rather than absolute. [seconds] is the number of seconds from the time of the request you wish the representation to be fresh for.
• s-maxage=[seconds] — similar to max-age, except that it only applies to shared (e.g., proxy) caches.
• public — marks authenticated responses as cacheable; normally, if HTTP authentication is required, responses are automatically uncacheable (for shared caches).
• no-cache — forces caches to submit the request to the origin server for validation before releasing a cached copy, every time. This is useful to assure that authentication is respected (in combination with public), or to maintain rigid freshness, without sacrificing all of the benefits of caching.
• no-store — instructs caches not to keep a copy of the representation under any conditions.
• must-revalidate — tells caches that they must obey any freshness information you give them about a representation. HTTP allows caches to serve stale representations under special conditions; by specifying this header, you’re telling the cache that you want it to strictly follow your rules.
• proxy-revalidate — similar to must-revalidate, except that it only applies to proxy caches.

For example:

Cache-Control: max-age=3600, must-revalidate

If you plan to use the Cache-Control headers, you should have a look at the excellent documentation in HTTP 1.1; see References and Further Information.