What are Core Web Vitals?
Core Web Vitals are Google's metrics for loading (LCP), responsiveness (INP) and visual stability (CLS), measured from real Chrome users.
Core Web Vitals are three metrics Google uses to describe a page's user experience: Largest Contentful Paint for loading, Interaction to Next Paint (INP) for responsiveness, and Cumulative Layout Shift (CLS) for visual stability. Each has a good threshold, assessed at the 75th percentile of real page loads.
| Metric | Measures | Good |
|---|---|---|
| LCP | Loading | 2.5 s or less |
| INP | Responsiveness | 200 ms or less |
| CLS | Visual stability | 0.1 or less |
LCP <= 2.5 s INP <= 200 ms CLS <= 0.1 (75th percentile)Google Search Central recommends achieving good Core Web Vitals, and says that this, along with other page experience aspects, aligns with what its core ranking systems seek to reward. Good scores do not guarantee rankings.
- TTFB is not a Core Web Vital, but it is part of LCP.
- Cache warming can improve LCP by removing origin time from TTFB. It does not change INP or CLS, which depend on scripts and layout.
- Google's field data comes from real Chrome users, wherever they are, so cold PoPs in any region where you have visitors count.
Related terms
References
- web.dev: Web Vitalshttps://web.dev/articles/vitals
- Google Search Central: Core Web Vitals and Google Search resultshttps://developers.google.com/search/docs/appearance/core-web-vitals
- web.dev: Largest Contentful Paint (LCP)https://web.dev/articles/lcp
Warm your cache after every deploy
sitewarm requests the pages in your sitemap after a deploy and reports the cache state the CDN returns for each one, with the vantage point it was measured from.