Cache-Control
The Cache-Control header provides directives that modify the default caching behavior for resources; allowing a normally non-cachable resource to be cached, or restricting or prohibiting caching of otherwise cachable resources (e.g. for privacy reasons).
Writing requests (clients)
The value of the Cache-Control request header is a list of cache directives, which is a token, and an optional argument. Request Cache-Control directives typically instruct the cache to make privacy considerations or to force a refresh. RFC 7234 lists the available request Cache-Control directives.
Cache-Control was introduced in HTTP/1.1, and might not be implemented by old HTTP caches, or caches that refuse to honor the Cache-Control header.
Reading requests (servers)
For the conditions when a cache may serve a cached response, see Caching.
Writing responses (servers)
RFC 7234 lists the available response Cache-Control directives
Cache-Control was introduced in HTTP/1.1, and might not be implemented by old HTTP caches, or caches that refuse to honor the Cache-Control header.
Reading responses (clients)
For the conditions when a cache may serve a cached response, see Caching.
Overview table
- Name
- Cache-Control
- Direction
- Both
- Specification
- RFC 9111: HTTP Caching §5.2. Cache-Control
Cache-Control is found in both directions, however the usage in either direction is different because of the different semantics of requests and responses.
Syntax
Cache-Control = delta-seconds
Example
Cache-Control: 3550
Here, the resource was returned from a cache, and the entry was populated just under an hour ago (just under 3600 seconds).
History
- 1999-06: RFC 2616 §14.9. Cache-Control
- 2014-06: RFC 7234 §5.2. Cache-Control
- 2022-06: RFC 9111 §5.2. Cache-Control