Simple definition
HTTP caching stores reusable responses according to cache headers, validators, and freshness rules.
Purpose and use
An HTTP cache avoids downloading or generating a representation again when a stored response can be reused.
How does it work?
Reuse depends on freshness, directives, validators and the cache key; Vary can distinguish response variants.
Example and verification
When visitors receive unexpected content, determine whether a shared cache incorrectly reuses a personalized response or another client's variant.
Points to watch
Purging a cache does not fix incorrect storage rules. Session or authentication-dependent content needs particular care with shared caches.
In short
Caching improves performance when reuse conditions respect the intended representation and user context.