Core Web Vitals are three metrics Google uses to describe the experience of loading and using a page:
| Metric | Measures | Good |
|---|---|---|
| LCP | Loading | 2.5 s or less |
| INP | Responsiveness | 200 ms or less |
| CLS | Visual stability | 0.1 or less |
A page passes when all three are good at the 75th percentile of real-user visits, as measured in the Chrome UX Report. INP replaced First Input Delay in March 2024.
Lighthouse measures LCP and CLS in the lab, and uses Total Blocking Time as a lab proxy for responsiveness. Use lab results to find and fix problems, and field data to confirm that real visitors see the improvement.