Core Web Vitals
Google's metrics measuring real-world user experience: loading performance, interactivity, and visual stability.
Definition
Core Web Vitals are Google's standardized metrics for measuring user experience, consisting of three specific measurements: Largest Contentful Paint (LCP) measures loading performance, First Input Delay (FID) measures interactivity, and Cumulative Layout Shift (CLS) measures visual stability.
These metrics became official Google ranking factors in 2021 as part of the Page Experience update. Google measures them using real user data (field data) from Chrome users, making actual user experience—not just lab scores—the determining factor.
Why It Matters
Core Web Vitals directly impact both rankings and user behavior. Slow, janky websites frustrate users and increase bounce rates, while fast, stable experiences improve engagement and conversion.
Google provides specific thresholds: LCP should be under 2.5 seconds, FID under 100 milliseconds, and CLS under 0.1. Meeting these benchmarks is increasingly important for competitive organic visibility.
Examples in Practice
An e-commerce site improves LCP from 4.2s to 2.1s through image optimization and CDN implementation, seeing a 15% decrease in bounce rate.
A news publisher fixes CLS issues caused by ad loading, improving user experience scores and maintaining ranking positions.
A SaaS company identifies slow server response as the LCP bottleneck and upgrades infrastructure, passing Core Web Vitals and improving conversions.