Core Web Vitals
Also known as: cwv, web vitals seo, core web vitals
Core Web Vitals are Google's standardized metrics for real-world page experience: Largest Contentful Paint (loading), Interaction to Next Paint (responsiveness), and Cumulative Layout Shift (visual stability). They factor into ranking.
- The three Core Web Vitals are LCP (loading), INP (responsiveness), and CLS (visual stability).
- INP replaced First Input Delay as the responsiveness vital in March 2024.
- Scores use real-user field data from CrUX at the 75th percentile, not lab tests alone.
The three metrics
Core Web Vitals are three field metrics Google tracks for every page. Largest Contentful Paint (LCP) measures how long the largest visible element takes to render; the "good" threshold is 2.5 seconds or less. Interaction to Next Paint (INP) measures responsiveness to taps, clicks, and key presses; "good" is 200 ms or less. INP replaced First Input Delay (FID) as a Core Web Vital in March 2024.
Cumulative Layout Shift (CLS) measures unexpected movement of visible content during load; "good" is a score of 0.1 or less. Together these cover loading, interactivity, and stability — the three things users feel most directly.
Field data vs lab data
Core Web Vitals are scored on field data (real user measurements) collected through the Chrome User Experience Report (CrUX), not synthetic lab runs. Google evaluates the 75th percentile of visits, so a page passes only when most real sessions are fast.
Tools like PageSpeed Insights, Search Console's Core Web Vitals report, and Lighthouse surface these scores. Lighthouse provides lab estimates for debugging, but ranking signals come from the field CrUX dataset.
Why it matters for site speed
Core Web Vitals are a confirmed (if lightweight) Google ranking signal and a strong proxy for user experience. Image weight is the most common LCP culprit, so optimizing hero images, using responsive images (srcset), and applying lazy loading to below-the-fold media are the highest-leverage fixes.
For an app's marketing and landing pages, passing Core Web Vitals keeps bounce rates low and protects search visibility — the same kind of efficiency Cleanor brings to a phone's storage.