Web Caching and Replication

5.10. Cacheability of Web Content

A response is called cacheable or uncacheable depending on whether or not it can be stored in a cache and used to satisfy future requests. Similarly, we call a request cacheable if it can be satisfied by a cached response, and uncacheable otherwise. In particular, a request to an uncacheable object is always uncacheable.

With a few exceptions, HTTP 1.1 provides a simple rule to decide whether a request or response is cacheable or not: the protocol allows any response to be cached and any request to be satisfied from a cached response, unless doing so is expressly prohibited by HTTP headers. In practice, however, requests and responses do not always include these headers, and proxies and other caches use heuristics, ...