Site Health Check
This article contains information about common WordPress Site Health checks, how WP Rocket can help, and how it's related to some of them.
WP_CACHE is set to false
The WP_CACHE is a WordPress native constant that enables or disables WordPress caching. It should be set to true to allow caching, specifically, WP Rocket's caching.
Some hosting providers, set this constant to false on purpose to use their caching instead, and in those cases, you can ignore this warning. However, sometimes this warning may indicate a real issue.
For specific guidance, please refer to the WP_CACHE is set to false article.
You should use a persistent object cache
In a few words, object caching is a mechanism to speed up the requests to the database directly on the server side, having a positive effect on the overall performance.
Object caching should be enabled and managed on the server side. And, while WP Rocket doesn't support this caching mechanism, WP Rocket and object caching can be used at the same time.
Please check our object caching guide for more information.
Browser caching
With browser caching, your site's assets will be stored in your visitors' browsers, after the first visit. It's important to enable browser caching to speed up the serving of the assets next time your visitors access your pages.
WP Rocket sets browser caching rules automatically via the .htaccess file for Apache and LiteSpeed servers, and on NGINX servers there are a couple of additional steps to follow.
Please check our guide for browser caching.
Your site could not complete a loopback request
A loopback request is a call that the server makes to itself. WordPress relies on this type of request to handle scheduled tasks.
WP Rocket's Preload feature relies on loopback requests. Therefore, if your site can't complete a loopback request, the Preload won't work.
If you see this warning, and since this implies server configuration, you should contact your hosting provider and ask them to fix this.
A scheduled event is late
Scheduled events are tasks that plugins, themes, and WordPress need to run in an asynchronous mode, and with a certain frequency. Common examples of scheduled events are the WordPress update checks, WooCommerce cancels unpaid orders and Site Health checks.
Many WP Rocket features rely on scheduled events, among the most important ones are Remove Unused CSS and Preload.
Therefore, it's key your site's scheduled events are running consistently. The easiest way to achieve this is by setting up a cron job on the server.
Even with the cron running consistently, you may see this warning if the queue of scheduled events is too long and some events don't run at the exact scheduled time. In such cases, and only if you've confirmed cron calls have a reliable frequency, you can ignore this warning as events should run once the queue size decreases.
Unable to detect the presence of page cache
This check depends on WordPress detecting any of these headers: cache-control, expires, last-modified, etag, x-cache-enabled, x-cache-disabled, x-srcache-store-status and x-srcache-fetch-status.
Besides having the page caching feature automatically enabled upon activation, WP Rocket will set the cache-control header on servers using an .htaccess file, but please refer to this guide if your site is failing this check.
Page cache is detected but the server response time is still slow
This warning can appear if the server response time is above 600 milliseconds.
In this case, it may be necessary to check the server for intermittent or sudden overload. Also, you should make sure plugins, themes and the PHP are updated to the newest versions available. Please see this article for more information.