Apache Reference: mod_expires, ExpiresActive
Trigger Expires Header Generation
Syntax: ExpiresActive on|off
Example: ExpiresActive on
Since: Apache 1.2
This directive enables or disables the generation of the Expires header. If found in an
.htaccessfile, for instance, it applies only to documents generated from that directory. If the directive is set to ``
on'', the Expires header will be added to served documents according to the criteria defined by the ExpiresByType and ExpiresDefault directives. Note that this directive does not guarantee the generation of an Expires header. If the criteria are not met, no header will be sent, just as if this directive had not been specified.