In short
Core Web Vitals are three metrics Google uses to quantify user experience: Largest Contentful Paint (LCP) for loading, Interaction to Next Paint (INP) for responsiveness, and Cumulative Layout Shift (CLS) for visual stability. The recommended targets are LCP under 2.5 seconds, INP under 200 milliseconds, and CLS under 0.1.
What Core Web Vitals measure
Core Web Vitals turn three vague feelings — is it loading, does it respond, does it hold still — into measurable numbers, gathered from real users. They are part of how Google assesses page experience, but their real value is that they correlate with whether people stay.
Largest Contentful Paint (LCP)
LCP measures loading: the time until the largest element in view — usually a hero image or heading — has rendered. Aim for under 2.5 seconds. The common fixes are serving right-sized, modern image formats, preloading the hero asset, cutting render-blocking scripts, and fast hosting.
Interaction to Next Paint (INP)
INP measures responsiveness: how quickly the page reacts, visibly, to taps and clicks across the whole visit. Aim for under 200 milliseconds. It is usually a JavaScript problem — break up long tasks, do less work on the main thread, and defer what is not needed for the first interaction.
Cumulative Layout Shift (CLS)
CLS measures visual stability: how much the layout jumps as the page loads. Aim for under 0.1. The fixes are mostly discipline — set explicit dimensions on images and embeds, reserve space for anything that loads late, and avoid inserting content above what the user is already reading.
Why they matter beyond Google
It is tempting to treat these as an SEO checkbox, but the numbers describe real experience. A fast LCP, a responsive INP, and a stable CLS are just what a considered product feels like — which is why we treat performance as a design constraint from the first screen, not a clean-up task before launch.
Common questions
What are the three Core Web Vitals?
Largest Contentful Paint (LCP), which measures loading; Interaction to Next Paint (INP), which measures responsiveness; and Cumulative Layout Shift (CLS), which measures visual stability.
What are good Core Web Vitals scores?
The recommended targets are LCP under 2.5 seconds, INP under 200 milliseconds, and CLS under 0.1, measured on real-world mobile traffic.
Do Core Web Vitals affect SEO?
Yes, they are part of how Google evaluates page experience, but their bigger effect is on users: faster, more stable pages keep more visitors and convert better regardless of ranking.