What are the Core Web Vitals?
Core Web Vitals are three metrics Google uses to describe how a page feels to real visitors: how fast the main content loads, how quickly the page reacts to input, and how stable the layout is.
The three Core Web Vitals
- Largest Contentful Paint (LCP): how long the largest text block or image takes to appear. Measures loading.
- Interaction to Next Paint (INP): how long the page takes to show a visual response after a click, tap or key press. Measures responsiveness. INP replaced First Input Delay (FID) as a Core Web Vital in March 2024.
- Cumulative Layout Shift (CLS): how much visible content jumps around while the page loads. Measures visual stability.
Thresholds
| Metric | Good | Needs improvement | Poor |
|---|---|---|---|
| LCP | up to 2.5 s | up to 4 s | over 4 s |
| INP | up to 200 ms | up to 500 ms | over 500 ms |
| CLS | up to 0.1 | up to 0.25 | over 0.25 |
A page passes the Core Web Vitals when the 75th percentile of real visits, measured separately for mobile and desktop, is in the Good range for all three metrics.
These scores come from real-user data. In LoadFocus you see them under Real-User Field Data, and you can alert on them. Lab runs measure Total Blocking Time as the closest stand-in for responsiveness. See Alert Metrics.