# Core Web Vitals — Optimization Reference A comprehensive guide to measuring, diagnosing, and fixing Core Web Vitals issues. These three metrics (LCP, INP, CLS) are Google's primary user experience signals and directly affect search rankings, ad Quality Score, and conversion rates. --- ## Thresholds Summary | Metric | Good | Needs Improvement | Poor | |---|---|---|---| | **LCP** (Largest Contentful Paint) | < 2.5s | 2.5s – 4.0s | > 4.0s | | **INP** (Interaction to Next Paint) | < 200ms | 200ms – 500ms | > 500ms | | **CLS** (Cumulative Layout Shift) | < 0.1 | 0.1 – 0.25 | > 0.25 | Google uses the 75th percentile of page loads (p75) from the Chrome UX Report (CrUX) for ranking signals. Optimizing for the median is not enough — you must bring the 75th percentile into the "good" range. --- ## LCP — Largest Contentful Paint ### What It Measures The render time of the largest visible content element in the viewport. LCP elements are typically: - `` elements (most common LCP element on the web) - `