What the numbers mean
The Chrome UX Report is Google’s public dataset of how real Chrome users experience sites. For each metric it gives the 75th percentile over the last 28 days, and how page loads split between good, needs improvement and poor.
| Metric | Measures | Good | Poor |
|---|---|---|---|
| LCP, Largest Contentful Paint | When the main content shows | up to 2.5 s | over 4 s |
| INP, Interaction to Next Paint | How fast the page reacts to taps and clicks | up to 200 ms | over 500 ms |
| CLS, Cumulative Layout Shift | How much the layout jumps while loading | up to 0.1 | over 0.25 |
| FCP, First Contentful Paint | When anything first shows | up to 1.8 s | over 3 s |
| TTFB, Time to First Byte | How long the server takes to start answering | up to 0.8 s | over 1.8 s |
A site passes the Core Web Vitals when LCP, INP and CLS are all good at the 75th percentile. FCP and TTFB aren’t part of the pass; they help explain a slow LCP.
Whole site or one page. The whole site pools every page, so it has data far more often. A single page needs enough Chrome traffic of its own.
Where to look when a metric is poor
- LCP: a large hero image loaded late, render-blocking CSS or fonts, or a slow TTFB. Preload the hero image, serve it at the right size, and cache HTML at the edge.
- INP: long JavaScript tasks on the main thread when someone taps. Split up heavy handlers, defer third-party scripts, and do less work per interaction.
- CLS: images and embeds without width and height, ads or banners inserted above content, and web fonts that swap late.
Third-party tags are a frequent cause of all three; the tracker detector lists what a page loads.
Measure it on your own site
This lookup only works for sites Chrome has enough data on, and only shows Chrome. invisit records LCP, INP, CLS, FCP and TTFB from your own visitors, from any browser that reports them, by page, country and device. It is a per-site switch in the dashboard; see the install options.