What are Core Web Vitals?
Core Web Vitals are three Google metrics, measured on real visits, for how a page loads, responds and holds still: Largest Contentful Paint, Interaction to Next Paint and Cumulative Layout Shift. A page passes when at least 75% of visits meet each target.
Cited from the66th.com/glossary/core-web-vitals
How Core Web Vitals work
Each metric covers one part of a visit. In web.dev's definitions, Largest Contentful Paint (LCP) measures loading performance, Interaction to Next Paint (INP) measures interactivity and Cumulative Layout Shift (CLS) measures visual stability. In plain terms: how soon the main content shows, how fast the page reacts to a tap, click or key press, and how much the layout jumps while it loads.
web.dev sets a target for each metric and recommends measuring at the 75th percentile of page loads, split by mobile and desktop. A page passes when it meets all three targets at that percentile, meaning at least three in four visits meet each one.
| Metric | What it measures | Good |
|---|---|---|
| Largest Contentful Paint (LCP) | Loading performance | Within 2.5 seconds of the page starting to load |
| Interaction to Next Paint (INP) | Interactivity | 200 milliseconds or less |
| Cumulative Layout Shift (CLS) | Visual stability | 0.1 or less |
Why Google cares
Google's Core Web Vitals guide says: "We highly recommend site owners achieve good Core Web Vitals for success with Search", and that good scores, along with other page experience aspects, align with what its core ranking systems seek to reward.
The scores come from the Chrome User Experience Report, which collects anonymized, real user measurement data and feeds PageSpeed Insights and the Core Web Vitals report in Google Search Console, Google's free tool for site owners.
What it means for your business
The metrics describe what your buyers live through: waiting for the main image, tapping a button that does nothing for a moment, or hitting the wrong link because the layout moved.
Passing all three will not lift a weak page to the top. Google's page experience guide says good results in reports don't guarantee top rankings, and that Google Search always seeks to show the most relevant content, even if the page experience is sub-par. Fix a failing metric on the pages buyers use, then put the effort into the content. Speed work is part of our technical SEO services.
Common mistakes
- Judging the site by one lab test. A single run on one device differs from real visits, and web.dev says lab measurement is not a substitute for field measurement.
- Still tracking First Input Delay (FID). INP replaced it as a Core Web Vital in 2024.
- Fixing the home page alone. Check the page types buyers land on, such as service pages, product pages and articles.
Related terms
Sources: web.dev, Web Vitals, 31 October 2024; Google Search Central, Understanding Core Web Vitals and Google search results, 10 December 2025; Google Search Central, Understanding Google page experience, 22 September 2026.