Core Web Vitals Checker withReal Field Data, Not Just a Lab Score
A live check against Google's PageSpeed Insights ; LCP, CLS, and INP from real visitors when available, plus Lighthouse Performance, Accessibility, Best Practices, and SEO scores.
One check prepares mobile and desktop together. Switch devices at any time. A fresh check may take up to a minute.
Step-by-step
How to use the Core Web Vitals Checker
Five steps from pasting a URL to knowing exactly what to fix first.
1.Paste the exact URL you care about
Core Web Vitals are measured per URL, not per site. Check the specific page ; a product page, a landing page ; not just your homepage.
2.Prepare both device reports
Click Check Core Web Vitals once. Mobile and desktop checks start together. Read the first result while the other device finishes.
3.Identify the measurement source
Field data describes real visitors. If it is unavailable, use labeled lab measurements for diagnostics. Lab TBT does not replace real-user INP.
4.Fix the worst-rated metric first
A page with one "Poor" metric and two "Good" ones usually gets more benefit from fixing the one weak spot than from marginally improving metrics that already pass.
5.Re-check after deploying a fix
Lab data updates immediately. Field data can take time to reflect a fix, since it's a rolling 28-day window of real visitor data ; don't expect the field numbers to move the same day.
Core Web Vitals best practices
- Optimize images for LCP. The largest content element ; usually a hero image ; is almost always the biggest lever for Largest Contentful Paint.
- Reserve space for images and embeds. Set explicit width/height (or aspect-ratio) on images and ads so they don't shift layout after loading ; the main driver of Cumulative Layout Shift.
- Break up long JavaScript tasks. Interaction to Next Paint suffers most from long-running scripts blocking the main thread when someone taps or clicks.
- Track trends, not single runs. A single lab score can swing between runs. Check back over days or weeks, and prioritize field data, which already averages real usage.
Common mistakes to avoid
- Optimizing only the homepage ; Core Web Vitals is evaluated per URL, and your highest-traffic landing pages matter more for rankings.
- Chasing a perfect lab score while ignoring field data ; a 100 lab score with poor field data means the lab test doesn't reflect real conditions for real visitors.
- Re-checking seconds after a deploy and expecting field data to already reflect it ; give the CrUX dataset time to update.
Before you act on a score
Field data vs. lab data
Compare real visitor measurements with a simulated Lighthouse test. Use field data to understand user experience and lab results to investigate specific improvements.
Field data is what Google ranks on
Field data comes from the Chrome User Experience Report ; real visitors, real devices, real networks, over the past 28 days. It's what Search Console's Core Web Vitals report is built from.
Lab data is one simulated run
Lab data is a single Lighthouse test under controlled, simulated network conditions. It's useful for debugging a specific page, but it can vary noticeably between runs and doesn't reflect your real traffic.
New or low-traffic pages have no field data
Google needs a minimum amount of real Chrome traffic before it publishes field data for a URL. A brand-new page will often show lab data only ; that's expected, not a bug.
Questions and answers
Core Web Vitals checker FAQ
Can I review the results before using them?
Yes. Review the output and highlighted issues before making changes to your website.
Why does it say no field data is available for my page?
Field data comes from the Chrome User Experience Report, which only publishes a URL once Google has collected enough real visitor data for it. New or low-traffic pages often show lab data only ; that's expected, not an error.
Why are my mobile and desktop scores so different?
Mobile and desktop runs use different test conditions and scoring. One check prepares both reports. Switch devices to view the matching result. Some pages may produce similar scores, so review the measurements and findings as well.
Does a perfect score guarantee good rankings?
No. Core Web Vitals is one of many ranking factors, and a good score removes a potential disadvantage rather than guaranteeing a boost. Treat this as a diagnostic tool, not a ranking predictor.