Lab scores on top, real users underneath.
Switch between Mobile and Desktop. The PageSpeed card shows the four Lighthouse category scores as gauges, colour-coded the way Google does it. Below that, each Core Web Vital from real Chrome users over the last 28 days, with its 75th-percentile value, a Good / Needs work / Poor rating and the distribution bar behind it.
- Performance, Accessibility, Best Practices, SEO – the PageSpeed Insights scores, 0–100.
- LCP – Largest Contentful Paint, how quickly the main content appears. Good is 2.5 s or under.
- INP – Interaction to Next Paint, how responsive the page feels when tapped. Good is 200 ms or under.
- CLS – Cumulative Layout Shift, how much the page jumps around while loading. Good is 0.1 or under.
- Each metric shows the share of real visits that were Good, Needs work and Poor.
Two kinds of speed data, and why you want both.
Real users (CrUX)
The Chrome UX Report aggregates what actual Chrome visitors experienced on your site over the previous 28 days, at the 75th percentile. This is the data Google uses for the Core Web Vitals report in Search Console and for the page experience signal. If it says Good, your real visitors are having a good time.
It needs enough traffic to exist: small sites may have no CrUX data at all, and the app says so rather than inventing a number.
Lab test (PageSpeed Insights)
Lighthouse loads your page in a controlled environment and scores it. The numbers vary from run to run and do not perfectly match what users see, but they come with the diagnostics that tell you what to fix, and they exist for any site, however small.
The app runs the test for mobile and desktop separately, because the results are usually very different.
Reading them together
Field Good and lab Poor: your audience has fast devices or connections, but new visitors on slower phones will not. Field Poor and lab Good: something in production (ads, third-party scripts, a slow region) is not in the lab test. Both Good: move on to the next thing.
Core Web Vitals and search.
Google uses page experience, including Core Web Vitals, as part of how it ranks pages. It is a tie-breaker rather than a headline factor: great content on a slow page still ranks, but between two comparable pages the faster one tends to win, and a Poor rating is worth fixing. Beyond ranking, slow pages lose visitors before they read anything, which shows up in the Performance report as a CTR that never converts into time on site.
What usually moves the numbers
- LCP – the hero image or the largest block of text. Compress and size images, preload the one that matters, keep render-blocking CSS small.
- INP – JavaScript. Heavy frameworks, third-party tags and long tasks on the main thread make taps feel sluggish.
- CLS – images without dimensions, late-loading fonts, ads and banners that push content down.
Where the data comes from
Real-user metrics come from the Chrome UX Report API for your origin; lab scores come from the PageSpeed Insights API. Both are requested directly from your iPhone with no server in between, and both are cached briefly so switching between Mobile and Desktop is instant.
Check your Core Web Vitals from your phone.
Real-user and lab data on one screen. Included with Pro, from £2.99 a month.
Download for iPhone