Core Web Vitals Checker Tool Online

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Run a GEO-ready Core Web Vitals audit for any URL. See field data when available, Lighthouse lab metrics, and clear LCP, INP, CLS verdicts that help search engines and AI systems trust fast pages.

Enter a URL to check Core Web Vitals:

How the Core Web Vitals Checker Works

This tool sends your URL to Google PageSpeed Insights, then separates real-user field data from Lighthouse lab measurements.

  1. URL validation, the API normalizes the address and checks that the host is public before making a request.
  2. PageSpeed Insights fetch, Google runs a mobile or desktop performance audit and returns CrUX plus Lighthouse data.
  3. Field metrics, the page-level CrUX values show LCP, INP, CLS, FCP, and TTFB when enough visitor data exists.
  4. Lab metrics, Lighthouse provides a controlled test with performance score, LCP, FCP, TBT, CLS, Speed Index, and server response time.

Why Core Web Vitals Matter

Core Web Vitals connect technical performance to user experience, SEO, and conversion quality.

  • Search visibility, Google uses page experience signals as part of ranking quality.
  • Conversion rate, faster loading and smoother interaction reduce abandonment on mobile.
  • AI discovery, fast, stable pages are easier for crawlers and answer engines to process.
  • Competitive diagnosis, this tool focuses on Core Web Vitals while our Website Performance Checker audits headers, compression, TTFB, and HTML patterns.

Core Web Vitals Thresholds

Aim for Good on all three Core Web Vitals at the 75th percentile of page loads.

MetricGoodNeeds workPoor
LCP
Largest Contentful Paint		≤ 2.5s2.5s to 4.0s> 4.0s
INP
Interaction to Next Paint		≤ 200ms200ms to 500ms> 500ms
CLS
Cumulative Layout Shift		≤ 0.10.1 to 0.25> 0.25

What to Fix First

Poor LCP usually needs image, hosting, font, and render-blocking fixes. Poor INP usually needs JavaScript reduction. Poor CLS needs reserved image, ad, and embed space. For implementation help, read our website speed optimization guide.

Next steps

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Core Web Vitals Checker: FAQ

What does the Core Web Vitals Checker measure?
It checks Google PageSpeed Insights data for LCP, INP, CLS, FCP, TTFB, Lighthouse performance score, and lab metrics for the URL you enter.
What are good Core Web Vitals scores?
Good thresholds are LCP at or below 2.5 seconds, INP at or below 200 milliseconds, and CLS at or below 0.1 at the 75th percentile of real user visits.
Why might field data be missing?
Field data comes from the Chrome User Experience Report. New, low traffic, or blocked pages may not have enough real user data, so the tool returns Lighthouse lab metrics only.
Should I test mobile or desktop?
Test mobile first because Google uses mobile-first indexing and many conversion problems happen on slower mobile devices and networks. Desktop is useful for B2B and office audiences.
How is this different from the Website Performance Checker?
The Website Performance Checker focuses on server and HTML signals like TTFB, compression, resource counts, and headers. This tool uses Google PageSpeed Insights for Core Web Vitals and Lighthouse lab scoring.
What is INP?
Interaction to Next Paint measures how responsive a page feels after user interactions. Heavy JavaScript, long tasks, and third-party scripts are common causes of poor INP.
How do I improve LCP?
Optimize the hero image, preload the main image or font, reduce server response time, remove render-blocking CSS and JavaScript, and serve content through a fast CDN.
How do I reduce CLS?
Set width and height on images, reserve space for ads and embeds, avoid late-loading banners, and avoid inserting content above existing content after the page starts loading.
Is this Core Web Vitals tool free?
Yes. It is free, runs in your browser through our API route, and does not require signup.

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