If-Modified-Since Header

@martychc23 For a long time, WordPress Core itself removed the If-Modified-Since header and when Comet Cache was originally written it followed that same behavior, because the If-Modified-Since header is tricky to do in such a dynamic environment like WordPress.

However, WordPress Core has since added support for sending the If-Modified-Since header (or rather, it has stopped automatically removing it), however Comet Cache has not yet been updated to support this.

We do plan to change this in a future release to allow the If-Modified-Since header and there’s a GitHub issue here with a comment describing the current state of Comet Cache + If-Modified-Since: https://github.com/websharks/comet-cache/issues/255#issuecomment-304394481

I recommend following that GitHub issue for updates.

You just need to make sure the following is in your .htaccess file (if this isn’t working, I recommend double-checking with your web hosting company, in case their server configuration is different):

<IfModule expires_module>
  ExpiresActive on
  ExpiresDefault "access plus 1 week"
</IfModule>

For static resources, your web server sends the If-Modified-Since headers with those requests. Requests for static resources don’t even go through PHP or WordPress, so Comet Cache wouldn’t have any effect on them.