Core Web Vitals are three metrics Google has used since 2021 to measure real user experience on a page. Unlike lab metrics such as PageSpeed scores, CWV are measured with real traffic via the Chrome User Experience Report (CrUX). The number that counts is the 75th percentile of your users, not a one-off Lighthouse run.
The three metrics
- LCP (Largest Contentful Paint): how long the largest viewport element takes to render. “Good” threshold ≤ 2.5 seconds. The load metric.
- INP (Interaction to Next Paint): latency between a user interaction and the next visual update. It replaced FID in March 2024. Good threshold ≤ 200 ms. The responsiveness metric.
- CLS (Cumulative Layout Shift): how much elements shift around during load. Good threshold ≤ 0.1. The visual stability metric.
Google flags the metric as “poor” above certain thresholds (LCP > 4s, INP > 500ms, CLS > 0.25). Between “good” and “poor” there is a “needs improvement” band.
Why they matter more than they seem
CWV are not a mega ranking factor in isolation. But they affect CTR indirectly (fast pages retain better), crawl budget (Googlebot prioritises fast sites), and measurable user experience (bounce rate, pages per session). When the rest of SEO is on par with competitors, CWV break the tie.
At SEOCOM we prioritise in this order: LCP first (direct impact on perceived speed), then CLS (impact on UX and trust), then INP (the hardest to optimise because it depends on third-party JS). Optimising the three at once without prioritising almost never works.