Core Web Vitals Checker
See how real visitors experience your page. Enter a URL and choose mobile or desktop to get the Core Web Vitals – Largest Contentful Paint, Interaction to Next Paint and Cumulative Layout Shift – from the Chrome UX Report, with the share of good, average and poor visits, the pass or fail assessment, a Lighthouse lab run and the improvements that would save the most time.
- Encrypted connection
- No sign-up
- Free to use
How to use Core Web Vitals Checker
- Enter the page URL.
- Choose mobile or desktop.
- Wait while Google tests the page (15–60 seconds).
- Review real-user data, lab results and opportunities.
Core Web Vitals Checker features
Real-user data
75th percentile from the Chrome UX Report.
Pass / fail
The same assessment Google uses for the page experience.
Distribution
Share of good, needs-improvement and poor visits.
Origin fallback
Site-wide data when the page has too little traffic.
Lab test
Lighthouse metrics and performance score.
Opportunities
The fixes with the biggest estimated saving.
When to use Core Web Vitals Checker
- Checking whether a page passes Core Web Vitals.
- Comparing mobile and desktop experience.
- Finding what slows the largest element down.
- Verifying improvements after a release.
Core Web Vitals Checker FAQ
Where do the numbers come from?
From Google PageSpeed Insights: real-user field data from the Chrome UX Report and a lab test Google runs. This site does not estimate or simulate the values.
What are the thresholds?
Good: LCP ≤ 2.5 s, INP ≤ 200 ms, CLS ≤ 0.1. Poor: LCP > 4 s, INP > 500 ms, CLS > 0.25. Each is measured at the 75th percentile of visits.
Why is there no field data?
The Chrome UX Report only includes pages and sites with enough Chrome visits. New or low-traffic pages show lab data only.
Why do lab and field results differ?
The lab test is one simulated visit on fixed hardware and network. Field data covers 28 days of real visitors on their own devices and connections.
Why does the tool sometimes say measurement is unavailable?
Google limits how often its API can be used. When the shared quota is used up, the tool says so instead of showing invented numbers.
Is INP measured in the lab?
No. INP needs real interactions, so it only appears in field data. Total Blocking Time is the closest lab indicator.
Understanding Core Web Vitals
Core Web Vitals are three measurements of user experience that Google uses as part of its page experience signals. Largest Contentful Paint measures how quickly the main content appears, Interaction to Next Paint measures how quickly the page responds to taps, clicks and key presses, and Cumulative Layout Shift measures how much content jumps around while loading.
What counts is real experience. Google collects anonymous timing data from Chrome users who opted in and publishes it in the Chrome UX Report. A page passes when at least 75% of visits are good for all three metrics, which is why the tool reports the 75th percentile.
Lab tests are still valuable for diagnosis. Lighthouse loads the page once under controlled conditions and lists concrete improvements, such as unused JavaScript or images that are too large, with an estimate of the time each would save.
Typical fixes are serving the main image quickly and in a modern format, reserving space for images and ads, reducing JavaScript that blocks the main thread and using a fast server or CDN. After a change, field data takes up to 28 days to reflect it fully.