Glossary

Core Web Vitals

Definition: Core Web Vitals are three Google metrics — LCP, INP and CLS — that measure real-world loading performance, interactivity and visual stability of web pages.

Core Web Vitals are a set of specific, real-world performance metrics introduced by Google as part of its Page Experience signals. They measure how users actually experience a page — loading speed, responsiveness and visual stability. Since 2021 they have been a confirmed Google ranking factor.

The Three Metrics

  • LCP — Largest Contentful Paint
    Measures loading performance: the time until the largest image or text block in the viewport is fully rendered.
    Good: < 2.5 s | Needs improvement: 2.5–4 s | Poor: > 4 s
  • INP — Interaction to Next Paint (replaced FID in 2024)
    Measures responsiveness: the delay between a user interaction and the next visual update.
    Good: < 200 ms | Needs improvement: 200–500 ms | Poor: > 500 ms
  • CLS — Cumulative Layout Shift
    Measures visual stability: the total amount of unexpected layout shifting during the page's lifespan.
    Good: < 0.1 | Needs improvement: 0.1–0.25 | Poor: > 0.25

How to Measure Core Web Vitals

  • Google Search Console → Core Web Vitals report.
  • PageSpeed Insights (pagespeed.web.dev).
  • Chrome DevTools → Lighthouse tab.
  • Chrome User Experience Report (CrUX) for field data.
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