Core Web Vitals Checker
Core Web Vitals are assessed from real visits at the 75th percentile, which is why a page that feels fast on your own machine can still fail. This check reports the field data Chrome has collected for the site next to a lab run, so you can see both whether you have a problem and what is causing it.
Results open in the site's full report, which you can share, compare and re-run.
What it checks
- Real-user LCP, INP and CLS from the Chrome UX Report, where Chrome has enough traffic to report them
- Lighthouse lab scores for mobile and desktop
- TTFB and total page weight
- Performance diagnostics with estimated savings, and the largest image transfers
- Third-party origins and how much they cost
Frequently asked questions
- What counts as a good score?
- LCP 2.5s or less, INP 200ms or less, CLS 0.1 or less — all three at the 75th percentile of real visits, measured separately for mobile and desktop.
- Why is there no field data for my site?
- The Chrome UX Report only publishes data for origins with enough traffic from Chrome users who opted into reporting. Smaller sites see lab results only.
- Why do the lab and field numbers disagree?
- A lab run is one simulated load on throttled hardware; field data is millions of real loads. Use the lab run to find the cause and the field data to decide whether it matters.
- How long until a fix shows up?
- Field data uses a 28-day rolling window, so improvements appear gradually and take roughly a month to be fully reflected. A lab run shows the effect immediately.
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