SEO & Search
What Are Core Web Vitals?
Three field metrics Google uses to describe loading, responsiveness and visual stability, measured on real visits rather than in a lab.
Definition
Core Web Vitals are three user experience metrics that Google publishes as a shared standard for page quality: Largest Contentful Paint for loading, Interaction to Next Paint for responsiveness, and Cumulative Layout Shift for visual stability. Each has a published threshold, and a site is assessed at the 75th percentile of real page loads.
The three metrics and their thresholds
Google defines a good result for each metric at the 75th percentile of page views, segmented across mobile and desktop.
- Largest Contentful Paint (LCP) should occur within 2.5 seconds of the page starting to load
- Interaction to Next Paint (INP) should be 200 milliseconds or less
- Cumulative Layout Shift (CLS) should be 0.1 or less
INP replaced First Input Delay
Interaction to Next Paint became a Core Web Vital in March 2024, replacing First Input Delay. FID measured only the delay before an interaction began processing. INP measures the full latency from interaction to the next frame painted, which reflects what a person actually perceives as sluggishness.
Field data and lab data are not interchangeable
Core Web Vitals are field metrics, collected from real Chrome users through the Chrome User Experience Report. Lab tools such as Lighthouse are useful for diagnosis but run one synthetic load on one connection profile, so they cannot reproduce a 75th percentile figure. Diagnose in the lab, but assess in the field.
To ensure you're hitting the recommended target for most of your users, a good threshold to measure is the 75th percentile of page loads, segmented across mobile and desktop devices.