Core Web Vitals Google's three measurable performance metrics—page load speed, interactivity, and visual stability—have been directly factored into the ranking since 2021.
The three metrics
- LCP (Largest Contentful Paint): how quickly the largest visible element (often a hero image or headline) loads. Target: under 2.5 seconds.
- INP (Interaction to Next Paint): how quickly the page responds to a click or tap. Target value: under 200 milliseconds.
- CLS (Cumulative Layout Shift): how stable the page appears while loading (does the content suddenly jump around?). Target value: below 0.1.
Field data vs. lab data
Google Measure Core Web Vitals not in a controlled test environment, but using real visitor data from the Chrome User Experience Report (CrUX), collected from people who actually visit the site on their own devices and internet connections. A page that scores perfectly in a lab test (such as Lighthouse) may still perform poorly in practice for visitors with a slow mobile connection.
Why This Is More Than Just a Technical Detail
Slow or unstable pages not only hurt your ranking, but also conversion: Visitors are more likely to leave a page that loads slowly, no matter how good the content itself is.
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