14.9.1 What is Cachable

By default, a response is cachable if the requirements of the request method, request header fields, and the response status indicate that it is cachable. Section 13.4 summarizes these defaults for cachability. The following Cache-Control response directives allow an origin server to override the default cachability of a response:

public

Indicates that the response is cachable by any cache, even if it would normally be non-cachable or cachable only within a non-shared cache. (See also Authorization, section 14.8, for additional details.)

private

Indicates that all or part of the response message is intended for a single user and MUST NOT be cached by a shared cache. This allows an origin server to state that the specified parts of the response are intended for only one user and are not a valid response for requests by other users. A private (non-shared) cache may cache the response.

Note: This usage of the word private only controls where the response may be cached, and cannot ensure the privacy of the message content.

no-cache

Indicates that all or part of the response message MUST NOT be cached anywhere. This allows an origin server to prevent caching even by caches that have been configured to return stale responses to client requests.

Note: Most HTTP/1.0 caches will not recognize or obey this directive.