Simple definition
The HTTP Cache-Control header defines directives controlling how browsers and intermediary caches store and reuse responses.
Purpose and use
Cache-Control expresses rules for storing and reusing an HTTP response in the relevant caches.
How does it work?
max-age defines freshness lifetime; no-cache requires validation before reuse, whereas no-store requests that the response not be stored.
Example and verification
For stale data, compare served directives, response age and browser or intermediary-cache behavior.
Points to watch
no-cache does not mean no storage. A caching directive is also neither cryptographic protection nor access authorization.
In short
Choose directives according to data sensitivity and update frequency, then verify their behavior along the actual delivery path.