Core Web Vitals

Core Web Vitals consist of Largest Contentful Paint (LCP, measures loading), First Input Delay (FID, measures responsiveness), and Cumulative Layout Shift (CLS, measures visual stability). Google introduced them as ranking factors in 2021 and incorporated them into the Page Experience signal, meaning poor vitals can hurt search visibility. The metrics are measured from actual user data collected via the Chrome User Experience Report, not lab tools alone.

For SEO practitioners, Core Web Vitals matter because they're a confirmed ranking factor and affect click-through rates—users bounce from slow or janky pages. Diagnosing poor vitals requires looking at real user data (in Search Console and Chrome DevTools) rather than just Lighthouse scores, since field performance varies by device and network. Common fixes include image optimization for LCP, reducing JavaScript for FID, and preventing layout shift through reserved space for ads, fonts, and dynamic content.