LCP, INP and CLS without the jargon — what each one measures, why Google cares, and how to fix a failing score.
Core Web Vitals are three measurements Google uses to judge whether your page feels good to use. They have intimidating names and very simple meanings.
LCP — how fast the main thing appears
Largest Contentful Paint measures how long it takes for the biggest visible element, usually your hero image or headline, to finish loading. Under 2.5 seconds is good. If you are failing, the culprit is almost always an oversized hero image, a slow server response or fonts blocking the render.
INP — how fast the page responds to a tap
Interaction to Next Paint measures the delay between someone tapping something and the page visibly reacting. Under 200 milliseconds is good. Heavy JavaScript is the usual cause — too many scripts fighting for the main thread while the user is trying to click.
CLS — how much the page jumps around
Cumulative Layout Shift measures content moving while the page loads. You know the feeling: you go to tap a link and an ad pushes it down. Keep it under 0.1 by setting width and height on images and reserving space for anything that loads late.
Where to check your scores
- PageSpeed Insights — quick test of a single page
- Search Console → Core Web Vitals — real visitor data across the whole site
- Chrome DevTools Lighthouse — good for testing fixes while you work
The order I fix them in
Images and server response first, because that fixes LCP and usually lifts everything. Then layout shift, which is cheap to fix and immediately noticeable. JavaScript last, because it takes the most care. Test on a real phone on mobile data — that is the experience Google is actually scoring.