Core Web Vitals measure loading, responsiveness and visual stability. Google uses them as part of a broader page experience signal.
The three metrics
- LCP, Largest Contentful Paint. When the main content becomes visible. Good: under 2.5 seconds.
- INP, Interaction to Next Paint. How quickly the page responds to input. Good: under 200 milliseconds. Replaced FID in 2024.
- CLS, Cumulative Layout Shift. How much the layout jumps while loading. Good: under 0.1.
Field data versus lab data
Google uses field data, real measurements from actual Chrome users, in the CrUX dataset. Lab tools such as Lighthouse are useful for diagnosis but are not what ranking uses. A perfect Lighthouse score with poor field data means your test conditions do not resemble your visitors.
How much weight
Google describes page experience as a tiebreaker rather than a primary factor. Content relevance dominates. A fast page with the wrong content does not outrank a slower page with the right content.
Alien Road recommends: fix LCP first and CLS second. LCP is usually a single oversized hero image or a render-blocking font, and both have cheap fixes. CLS is usually images without dimensions and injected banners. INP is worth attacking only after those two, because it typically means real JavaScript work.