Core Web Vitals: User-Centric Performance
Core Web Vitals measure real user experience. Google uses them as ranking signals, and they directly correlate with user satisfaction and conversion rates.
The Three (Now Four) Vitals
| Metric | Measures | Good | Poor |
|---|---|---|---|
| LCP (Largest Contentful Paint) | Loading performance | ≤2.5s | >4.0s |
| INP (Interaction to Next Paint) | Interactivity | ≤200ms | >500ms |
| CLS (Cumulative Layout Shift) | Visual stability | ≤0.1 | >0.25 |
| FID (First Input Delay) | First interactivity (deprecated) | ≤100ms | >300ms |
LCP: Largest Contentful Paint
Time until the largest visible element renders. Usually:
- <img> elements
- Video poster images
- Background images via CSS
- Block-level text elements