Caching / no-cache (RFC 7234)
The "no-cache" request directive indicates that a cache MUST NOT use a stored response to satisfy the request without successful validation on the origin server. The "no-cache" response directive indicates that the response MUST NOT be used to satisfy a subsequent request without successful validation on the origin server. This allows an origin server to prevent a cache from using it to satisfy a request without contacting it, even by caches that have been configured to send stale responses.