Core Web Vitals Explained: LCP, INP, and CLS / Jun 28, 2026
Core Web Vitals are Google's way of turning "does this site feel good to use" into numbers. There are three, each covering a different part of the experience, and each has a clear target you can aim for.
Largest Contentful Paint (loading)
LCP measures how long it takes for the biggest visible element, usually a hero image or heading, to appear. The target is under 2.5 seconds. Common fixes are serving the right image size in a modern format, preloading the hero, rendering content on the server, and cutting render blocking scripts and fonts.
Interaction to Next Paint (responsiveness)
INP measures how quickly the page responds when someone taps or clicks. The target is under 200 milliseconds. It suffers when the main thread is busy, so the fixes are shipping less JavaScript, breaking up long tasks, and moving heavy work off the main thread. Animations should use transform and opacity, never layout properties.
Cumulative Layout Shift (stability)
CLS measures how much the page jumps around as it loads. The target is under 0.1. It is almost always caused by content that arrives without reserved space. Give images and embeds fixed dimensions, load fonts without a swap that reflows text, and never insert banners above content that has already rendered.
How to measure
Use field data, not just lab data. Lab tools like Lighthouse are useful for debugging, but Google ranks on what real users experience, which you can see in the Chrome User Experience Report and Search Console. Test on a mid range phone on a normal connection, because that is closer to your real audience than your fast laptop.
Chasing a perfect Lighthouse score is a trap. Chase the three real metrics on real devices, fix the biggest offender first, and re measure. Small, steady improvements to loading, responsiveness, and stability compound into a site that feels fast and ranks well.
Frequently asked questions
- What are the Core Web Vitals?
- They are three metrics Google uses to measure real user experience: Largest Contentful Paint for loading, Interaction to Next Paint for responsiveness, and Cumulative Layout Shift for visual stability.
- What are good Core Web Vitals scores?
- Aim for Largest Contentful Paint under 2.5 seconds, Interaction to Next Paint under 200 milliseconds, and Cumulative Layout Shift under 0.1, measured on real mobile devices.
- Do Core Web Vitals affect SEO?
- Yes. They are a ranking signal and, more importantly, they reduce abandonment. Faster, more stable pages keep more visitors and tend to perform better in search.