Cache-Control官方文档

https://tools.ietf.org/html/draft-ietf-httpbis-p6-cache-25#page-21

5.2. Cache-Control


   The "Cache-Control" header field is used to specify directives for

   caches along the request/response chain.  Such cache directives are

   unidirectional in that the presence of a directive in a request does

   not imply that the same directive is to be given in the response.

   A cache MUST obey the requirements of the Cache-Control directives

   defined in this section.  See Section 5.2.3 for information about how

   Cache-Control directives defined elsewhere are handled.

      Note: Some HTTP/1.0 caches might not implement Cache-Control.

   A proxy, whether or not it implements a cache, MUST pass cache

   directives through in forwarded messages, regardless of their

   significance to that application, since the directives might be

   applicable to all recipients along the request/response chain.  It is

   not possible to target a directive to a specific cache.

   Cache directives are identified by a token, to be compared case-

   insensitively, and have an optional argument, that can use both token

   and quoted-string syntax.  For the directives defined below that

   define arguments, recipients ought to accept both forms, even if one

   is documented to be preferred.  For any directive not defined by this

   specification, a recipient MUST accept both forms.

     Cache-Control   = 1#cache-directive

     cache-directive = token [ "=" ( token / quoted-string ) ]

   For the cache directives defined below, no argument is defined (nor

   allowed) unless stated otherwise.

5.2.1. Request Cache-Control Directives

5.2.1.1. max-age


   Argument syntax:

      delta-seconds (see Section 1.2.1)

   The "max-age" request directive indicates that the client is

   unwilling to accept a response whose age is greater than the

   specified number of seconds.  Unless the max-stale request directive

   is also present, the client is not willing to accept a stale

   response.

   This directive uses the token form of the argument syntax; e.g.,

Fielding, et al.          Expires May 21, 2014                 [Page 21]

Internet-Draft              HTTP/1.1 Caching               November 2013

   'max-age=5', not 'max-age="5"'.  A sender SHOULD NOT generate the

   quoted-string form.

巴特西

Cache-Control官方文档

5.2. Cache-Control

5.2.1. Request Cache-Control Directives

5.2.1.1. max-age

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