When certain HTTP/1.1 origin servers receive an HTTP/1.0 request (e.g., from Squid), and the response contains a Vary header, they also add an Expires header set to the current time. This is to prevent HTTP/1.0 caches, which may not understand the Vary header, from incorrectly reusing a cached response.

Squid understands and implements the Vary header but still sends the string "HTTP/1.0" in its requests. You'll need to enable this directive if you want to get cache hits from responses with Vary and with Expires equal to Date. This directive is somewhat dangerous because the origin server may have its own reasons (other than maintaining backward compatibility) for setting the Expires header.


vary_ignore_expire on|off


vary_ignore_expire off


vary_ignore_expire on

    Appendix A. Config File Reference