What It Is
Google measures three things about the experience of using a page, and names them the Core Web Vitals:
- Largest Contentful Paint (LCP): how long a visitor waits before the biggest thing on the screen, usually the headline or the main photo, has finished drawing. Good is 2.5 seconds or less.
- Interaction to Next Paint (INP): how quickly the page responds when someone taps a button or a menu. Good is 200 milliseconds or less.
- Cumulative Layout Shift (CLS): how much the page jumps around while it loads, the moment a button moves just as your thumb lands on it. Good is 0.1 or less.
How It Works
These numbers come from real visits. Chrome users who have agreed to share usage statistics report how pages actually behaved on their devices, and Google publishes the result over a rolling 28 days. A page passes when at least three in four visits (the 75th percentile) meet the good threshold on all three. You can see your own pages' results in PageSpeed Insights and in the Core Web Vitals report in Search Console. A small site may not have enough visits for Google to report page by page, in which case Google reports the site as a whole or not at all.
This is different from a lab test like Lighthouse, which loads the page once on a simulated phone. Lab tests are useful for finding causes. Field data is the verdict, because it is what your customers lived through.
Why It Matters for Being Found
Google says plainly that it always tries to show the most relevant result, even when that page is slow. So speed will not lift a page that does not answer the search. But when several local businesses answer it equally well, Google says a good page experience can contribute to success, and Core Web Vitals are part of how it measures that experience. The larger effect is on people. A customer on a phone in a parking lot does not wait for a slow page. They tap the next result.