Core Web Vitals
Also called CWV, page experience signals
A set of three field-measured metrics Google uses to describe page experience: Largest Contentful Paint for loading, Interaction to Next Paint for responsiveness, and Cumulative Layout Shift for visual stability.
Three metrics, each measuring a different kind of annoyance.
Largest Contentful Paint (LCP) — how long until the biggest thing above the fold is drawn. This is “did the page appear”.
Interaction to Next Paint (INP) — how long the page takes to respond visibly after a user interacts. This is “did the page listen”.
Cumulative Layout Shift (CLS) — how much the layout moves around after it first draws. This is “did the page stay still while I was reading it”.
Lab is not field. A Lighthouse run is a synthetic measurement on one machine under one network profile. Core Web Vitals as Google uses them are field data from real visits. A perfect lab score with poor field data usually means your real users are on worse devices and networks than your test.
Keep the weighting honest. These are a real signal and a small one. Fixing a page that takes six seconds to render is worth doing for its own sake. Chasing a score from 92 to 96 rarely moves a ranking, and netweft prices the per-page performance check at 50 credits partly so that the cost of chasing it is visible before you start. What that does to a full crawl is worked through in what a 500-page crawl costs.
Last reviewed . Also served as markdown at /glossary/core-web-vitals.md.