Frontend
What is Web Vitals?
Google's user-centric performance metrics—LCP, INP, and CLS—that quantify loading speed, interactivity, and visual stability.
Definition
Core Web Vitals are three field metrics Google uses as a ranking signal: Largest Contentful Paint (loading; good under 2.5s), Interaction to Next Paint (responsiveness; good under 200ms, replacing First Input Delay in 2024), and Cumulative Layout Shift (visual stability; good under 0.1). Scores come from real Chrome users via the CrUX dataset, measured at the 75th percentile—lab tools like Lighthouse only approximate them. Common fixes include preloading the LCP image, breaking up long JavaScript tasks, reserving space for ads and embeds, and using font-display: swap with size-adjusted fallbacks.