Overview#

HTTP Cache Directive are parameters for the HTTP Header Field Cache-Control

HTTP Cache Directives are Case-insensitive and have an optional argument, that can use both token and quoted-string syntax. Multiple directives are comma-separated.

HTTP Cache Directives are defined in the IANA Registry Hypertext Transfer Protocol (HTTP) Cache Directive Registry

!! HTTP Request Header Cache-Control HTTP Cache Directive#

Standard HTTP Cache Directive directives that can be used by the client in an HTTP Request.

• Cache-Control: max-age=<seconds>
• Cache-Control: max-stale[=<seconds>]
• Cache-Control: min-fresh=<seconds>
• Cache-control: no-cache - Forces caches to submit the request to the origin server for validation before releasing a cached copy.
• Cache-control: no-store
• Cache-control: no-transform
• Cache-control: only-if-cached - Indicates to not retrieve new data. The client only wishes to obtain a cached response, and should not contact the origin-server to see if a newer copy exists.

HTTP Response Header Cache-Control HTTP Cache Directive #

Standard HTTP Cache Directive directives that can be used by the server in an HTTP Response

• Cache-control: must-revalidate - The cache must verify the status of the stale resources before using it and expired ones should not be used.
• Cache-control: no-cache - Forces caches to submit the request to the origin server for validation before releasing a cached copy.
• Cache-control: no-store - Indicates to not retrieve new data. The client only wishes to obtain a cached response, and should not contact the origin-server to see if a newer copy exists.
• Cache-control: no-transform
• Cache-control: public - Indicates that the HTTP Response may be cached by any cache.
• Cache-control: private - Indicates that the response is intended for a single user and must not be stored by a shared cache. A private cache may store the response.
• Cache-control: proxy-revalidate
• Cache-Control: max-age=<seconds>
• Cache-control: s-maxage=<seconds>

Extension HTTP Cache Directive HTTP Cache Directive #

Extension HTTP Cache Directive directives are not part of the core HTTP caching standards document. Be sure to check the compatibility table for their support.

• Cache-control: immutable
• Cache-control: stale-while-revalidate=<seconds>
• Cache-control: stale-if-error=<seconds>

More Information#

There might be more information for this subject on one of the following:

• Cache-Control
• HTTP Header Directive
• HTTP Header Field

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• [#1] - Cache-Control - based on information obtained 2017-01-05