P3 Plugin Profiler Says WP Rocket Uses The Most Resources
P3 Plugin Profiler can be a useful tool in diagnosing slow websites, but it's also easy to misunderstand. P3 Profiler attempts to measure how much of your total page loading time can be attributed to each plugin. But when using a caching plugin, P3 provides very misleading results. When you use a cache plugin, it loads before everything else and will appear to take up all the resources, but in fact it's because it's replacing all the normal processes that WordPress would typically have to run through when loading your site.
How does a caching plugin like WP Rocket work?
WP Rocket takes all the content of a given webpage and stores it as a single, static HTML file which is displayed to your visitors. Serving a static HTML file is much faster than the normal loading of a WordPress page which involves executing PHP, making calls to the database etc.
So, since WP Rocket is replacing all those other functions, P3 reports that it is using the most resources. It doesn't show that this is what is making your site FASTER, not slower!
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