Free tool

Core Web Vitals Checker: Test Real-World Website Performance

Seed Light built this free Core Web Vitals checker to show Google's figures for loading, responsiveness and visual stability. The figures come from real Chrome users where enough public data exists.

See LCP, INP and CLS from Google's real-user data, with each metric explained in plain words.

Free to use, with no sign up. The address and result may stay in our server cache for up to ten minutes. Speed checks use Google PageSpeed Insights.

The method

What the checker looks at

01
The numbers come from real visitors
Google's Chrome User Experience Report aggregates what real Chrome users experienced over the previous 28-day collection period. Nothing here is simulated.
02
Three measures, three plain questions
Did the main content appear quickly. Did the page respond when someone tapped. Did the layout stay still while someone was reading it.
03
Not every URL has enough public data
If Google does not publish enough CrUX data for the URL or origin, the checker shows that clearly instead of treating missing data as a poor score.
04
Page and origin data are labelled separately
Where Google publishes enough data for the exact URL, we report that. Where it does not, we report the origin and say so, because those are two different claims.

See how we keep sites healthy

Straight answers

Common questions

Common questions about what this check can and cannot tell you.

No data means Google does not publish enough eligible Chrome User Experience Report visits for that URL or origin in the current collection period. It does not mean the website is slow. Use a lab test for diagnostics while field data is unavailable.

Core Web Vitals and speed tests use different data. CrUX reports real visitor experiences collected over time, while a speed test measures one simulated visit under set conditions.

LCP measures how quickly the main visible content loads. INP measures how promptly the page responds after someone interacts with it. CLS measures how much content moves unexpectedly while the page is loading.

Fix the metric failing for the largest share of users first. Then use a lab test to identify the page element or script causing it.

Field data uses a rolling 28-day period, so a change appears gradually as newer visits replace older ones. A full before-and-after view can take four weeks.

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