Core Web Vitals (CWV) are three performance metrics that Google uses as a ranking signal under the Page Experience framework. They measure user-perceived quality of a web page — not just technical performance.
The three metrics
LCP (Largest Contentful Paint) measures how quickly the main content of a page loads. A good LCP is under 2.5 seconds. It typically corresponds to the hero image or primary heading.
INP (Interaction to Next Paint) measures the responsiveness of a page to all user interactions across the full page visit. A good INP is under 200ms. INP replaced the older FID metric in March 2024.
CLS (Cumulative Layout Shift) measures how much page content moves unexpectedly after initial load. A good CLS score is under 0.1. High CLS causes users to click the wrong elements.
Why they matter for SEO
Google confirmed Core Web Vitals as a ranking factor in the May 2021 Page Experience update. They function as a tiebreaker: when two pages have similar relevance and authority, the one with better CWV scores is more likely to rank higher. For competitive queries, they can directly influence position.
Google measures CWV from real Chrome users via the Chrome UX Report (CrUX) — not from simulated tests. Your Search Console CWV report shows how your pages actually perform for real visitors.
How to check your scores
Use Google PageSpeed Insights to see both lab data (Lighthouse) and field data (CrUX). Field data is what Google uses for ranking. Focus your optimisation work on field data scores, particularly for mobile users.
Related terms
- LCP (Largest Contentful Paint) — the load speed metric
- Page Speed — broader page performance concept
- Technical SEO — the category Core Web Vitals falls under
