Performance
Core Web Vitals Explained: LCP, INP & CLS in 2026
The Three Core Metrics
Google's Core Web Vitals are the page experience signals that directly influence ranking. In 2026, the three active metrics are Largest Contentful Paint (LCP), Interaction to Next Paint (INP), and Cumulative Layout Shift (CLS).
| Metric | Good | Needs Improvement | Poor |
|---|---|---|---|
| LCP | ≤ 2.5 s | 2.5 – 4 s | > 4 s |
| INP | ≤ 200 ms | 200 – 500 ms | > 500 ms |
| CLS | ≤ 0.1 | 0.1 – 0.25 | > 0.25 |
Largest Contentful Paint (LCP)
LCP measures how long it takes for the largest visible element (usually a hero image or heading) to render. Optimise by preloading the LCP resource, using a CDN, and compressing images to modern formats like AVIF or WebP.
Common LCP Culprits
Render-blocking CSS, unoptimised fonts loaded via @font-face, and large above-the-fold images without fetchpriority="high" are the most frequent LCP offenders.
Interaction to Next Paint (INP)
INP (which replaced FID in March 2024) measures end-to-end responsiveness for all user interactions. Long JavaScript tasks and heavy event handlers are the primary causes of high INP scores.
Cumulative Layout Shift (CLS)
CLS quantifies visual instability — how much page content unexpectedly shifts during load. Reserve explicit dimensions for images, videos, and ads to prevent layout reflows.
Measuring CWV
Use the Chrome User Experience Report (CrUX) for real-world field data, and Lighthouse / PageSpeed Insights for lab diagnostics. Field data is what Google uses in ranking.
Continuous Monitoring
CWV can regress with any deploy. Integrate Lighthouse CI into your CI/CD pipeline and set budget thresholds to fail builds that introduce regressions.
Tooling
PageSpeed Insights · web.dev Metrics · Chrome UX Report
Xeopix check
Xeopix reports CrUX field data alongside our static audit results, giving you both lab and real-world performance context in one dashboard.