id,summary,reporter,owner,description,type,status,priority,milestone,component,version,severity,resolution,keywords,cc,focuses 54423,Add Site Health test for full page caching (advanced cache),westonruter,,"A [https://make.wordpress.org/hosting/handbook/performance/#full-page-cache best practice] for performance is to enable full page caching for a WordPress site. Doing so reduces the time to first byte (TTFB) and thus directly impacts Core Web Vitals. This is especially important on shared hosts which have limited compute power, while also protecting a site from going down due to traffic spikes. As with XML Sitemaps, it may make sense for WordPress core to include a basic full page caching solution out of the box which can be extended by the many plugins that provide page caching today. In the meantime, there should at least be a Site Health test with a low-severity `recommended` status to point users to where to go to enable page caching. Since hosts often have built-in caching solutions in place, the Site Health test should be easily filterable so they can provide a link to their specific dashboard or documentation to enable caching which may not be a plugin at all but rather a reverse proxy like Varnish. In the context of the AMP plugin for WordPress, we've already developed such a test which could be adapted for core. See [https://github.com/ampproject/amp-wp/pull/6456 amp-wp#6456]. It's an async test which issues three loopback requests to the homepage, and the test will pass if responses include either of the following headers: 1. `Cache-Control` with non-zero `max-age`. 2. `Expires` with a future time. 3. `Age` with a positive number (as is set via a proxy like Varnish).",enhancement,closed,normal,,Site Health,,normal,duplicate,needs-docs,,performance