The following excerpt is taken from Optimizing WordPress for Web Core Vitals. You can read the introduction to the guide here.
Google’s PageSpeed Insights tool measures six key elements of site speed — we’ll get into each one in detail later — and compiles them into a PageSpeed score, which is graded on a 0-100 scale.
The general idea is that a site that scores 90, which is the benchmark for a “green light” from PageSpeed Insights, is in the 90th percentile of all sites on the Internet in terms of speed. In other words, that site is faster than 90 percent of all sites on the Internet. (Google has pegged specific speed thresholds to accomplish each score, but it is possible they will change these in the future — for example, if all sites on the web are faster two years from now, the 90th-percentile scores may require faster load times to achieve.)
Want to see how your site scores today? Just paste your URL into PageSpeed Insights and wait a few seconds for Google to work its magic. Your home page will generally score worse than mostly-text pages like blog posts, so try a few key pages to get a sense of where you stand overall.
I’m pretty proud of our scores, so I’ll share them here:
These are the scores that Google assigns based on the simulated experience on a 4G mobile device (which is probably slower than your current phone, especially if you’re on WiFi) — and it’s those mobile scores that will matter for your rankings. Desktop scores are also available, but it’s much easier to score high on desktop, and that score won’t matter for SEO rankings, so we’ll focus exclusively on mobile in this guide.
You may see your score vary by a few points each time you try it — this is usually a result of the response time of your web server changing from moment to moment. If you see dramatic shifts, that’s probably a sign you have a shaky infrastructure under your site (we’ll get to fixing that soon).
We were able to get our home page — which is a large, long page full of elaborate designs and imagery – scoring almost as high as our blog posts by following the steps I’ll be outlining in this guide. While I think it’s acceptable to score a little lower on a home page, since it’s typically not going to be your highest-traffic page in terms of organic search traffic, Google will be judging your site based on the aggregate score of all your pages so you can’t focus solely on your biggest SEO landing pages. You need to take a holistic approach and speed up every page on your site to get the biggest benefit from Core Web Vitals.
If you’re not in the 90th percentile or above, you’ll get a yellow or red score from Google and you’ll soon be demoted in the rankings as a result. As of this writing, we haven’t seen the exact way Google will “flag” sites as fast or slow, but you can count on it being significant. For example, a few years back they started adding a giant red “NOT SECURE” badge to sites that didn’t use modern SSL certificates, which, as you might imagine, really freaked people out. It would not surprise me if we saw similar labels for fast and slow sites in the future.
The 90th percentile is by no means impossible to achieve, but it’s very unlikely your site is in that zone now if you haven’t done explicit work on Core Web Vitals already. In fact, there’s a good chance that many of your pages are in the red (49th percentile and below) – so let’s get to work on making them lightning-fast instead.