Core Web Vitals are Google's page experience metrics measuring real-world user performance. The three vitals are Largest Contentful Paint (LCP, loading speed; target under 2.5s), Interaction to Next Paint (INP, responsiveness; target under 200ms) and Cumulative Layout Shift (CLS, visual stability; target under 0.1). Core Web Vitals are a Google ranking factor and are increasingly weighted by AI agents that prefer fast-rendering sources.
LCP times how long the largest visible element takes to render. INP measures the delay between a user interaction and the resulting visual update. CLS measures unexpected layout shifts during page load.
LCP: optimize images, preload critical assets, server-side render, use CDN. INP: minimize main-thread blocking, defer non-critical JS, use input delay budget. CLS: declare width/height on images, reserve space for ads, avoid inserting content above viewport.
Use Google's PageSpeed Insights (which is integrated into the free Readiness Check). For real-user data, use Search Console's Core Web Vitals report which uses Chrome User Experience data.
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