Core Web Vitals are Google’s way of putting numbers on how a page feels to use. There are three, and each has a “good” threshold measured at the 75th percentile of real visits, so at least three out of four visitors need a good experience for the page to pass:
| Metric | Measures | Good | Poor |
|---|---|---|---|
| Largest Contentful Paint (LCP) | How fast the main content appears | 2.5 s or less | Over 4 s |
| Interaction to Next Paint (INP) | How quickly the page responds to taps and clicks | 200 ms or less | Over 500 ms |
| Cumulative Layout Shift (CLS) | How much the layout jumps around | 0.1 or less | Over 0.25 |
INP replaced First Input Delay (FID) as a Core Web Vital in March 2024. Any guide still talking about FID is out of date.
How much they affect rankings
Core Web Vitals are part of Google’s page experience signals, and Google has been clear that they are a small factor next to relevance and content quality. A fast page with thin content won’t outrank a slower page that answers the question far better. Where they matter more is with visitors. Coastline Plumbing’s emergency page, opened on a phone by someone standing in a flooded kitchen, has a few seconds to show a phone number before the visitor goes back and taps a competitor.
Field data versus lab data
Google uses field data: measurements from real Chrome users, collected in the Chrome User Experience Report (CrUX) over a rolling 28 days. Tools like Lighthouse produce lab data from a single simulated load. Lab scores are useful for debugging, but the field numbers are what count. A low-traffic page may have no field data at all, in which case Google groups it with similar pages or uses the site-wide figure.
How to check
- Search Console’s Core Web Vitals report groups your URLs into Good, Needs improvement and Poor, separately for mobile and desktop.
- PageSpeed Insights shows field data for a URL or origin plus a Lighthouse lab test with specific fixes.
- RankThat’s Site Audit includes speed and Core Web Vitals checks across your pages, and each issue explains what to fix.
Common mistakes
Chasing a perfect Lighthouse score of 100 while field data is already good wastes effort. So does testing only the homepage. Product, service and blog templates often have very different problems, and those are usually the pages people land on from search. Start with the template that has the most “Poor” URLs and fix it once for all of them. Slow server response, measured as TTFB, is often the root cause behind a poor LCP.