Everyone knows this: a page loads too slowly, stutters while scrolling, or a button jumps away at the last moment. You get annoyed and you're gone. That is exactly what Google measures with the Core Web Vitals, and exactly that goes into how your page is rated.
There are three metrics. Don't worry, this stays easy to follow.
LCP: how fast is the most important part there?
LCP stands for Largest Contentful Paint. It measures how long it takes until the largest visible content has loaded, usually the main image or the headline. Target: under 2.5 seconds. Anything above that feels sluggish.
INP: how fast does the page respond?
INP stands for Interaction to Next Paint. It measures how fast the page responds to an action, for example a click. Target: under 200 milliseconds. If you click and nothing happens at first, the value is bad.
CLS: does everything stay in place?
CLS stands for Cumulative Layout Shift. It measures how much the page jumps around while loading. You know it: you're just about to tap something and suddenly everything shifts. Target: under 0.1.
Why it matters
Two reasons. First, people: slow pages get clicked away, often before they've even finished loading. Second, Google: the Core Web Vitals are a real ranking factor. So a fast page has it twice as easy.
What usually causes it
- Images that are too large and not optimized.
- Too much JavaScript working in the background.
- Slow or overloaded hosting.
- Website builder pages that drag a lot of dead weight along.
The good news: all of this can be fixed. That's exactly why I build pages by hand instead of with a website builder, so only what's needed is in there.
How this fits into the bigger picture is covered in SEO explained simply. If you want to know how your site scores on these metrics, take a look at my SEO and GEO analysis.