Core Web Vitals Checker
Test LCP, CLS, INP, FCP, and TTFB for mobile and desktop — powered by Google PageSpeed Insights.
Enter any public URL and click Analyze to test Core Web Vitals — LCP, CLS, INP, FCP, and TTFB for both mobile and desktop using Google PageSpeed Insights.
Analysis is performed via GET /api/v1/seo/pagespeed. Results take up to 30 seconds as Google runs a full lab test.
What is Core Web Vitals Checker?
Core Web Vitals Checker runs a full Google PageSpeed Insights analysis on any public URL and shows every Core Web Vitals metric side-by-side for mobile and desktop. It measures the five signals Google uses as ranking factors: LCP (Largest Contentful Paint) — how quickly the main content loads; CLS (Cumulative Layout Shift) — how stable the layout is while loading; INP (Interaction to Next Paint) — how fast the page responds to clicks and taps; FCP (First Contentful Paint) — how quickly the first visible content appears; and TTFB (Time to First Byte) — how fast your server responds.
Each metric is colour-coded against Google's official thresholds — green for Good, amber for Needs Improvement, and red for Poor — so you can see exactly which signals to fix first. The performance score (0–100) mirrors what Google uses when evaluating page experience for ranking. A score of 90+ is Good, 50–89 Needs Improvement, and below 50 is Poor. No signup, no install, no limit on URLs — paste any public page and get results in under 30 seconds.
Common Use Cases
- Testing a page's Core Web Vitals before and after a performance optimisation
- Checking if poor LCP or CLS is hurting your Google ranking
- Comparing mobile vs desktop performance scores for any page
- Auditing a client website for page experience issues before delivery
- Benchmarking competitor pages to identify performance advantages
How to Use Core Web Vitals Checker
- Enter the full URL of the page you want to test.
- Click Analyze — the tool runs Google PageSpeed for both mobile and desktop in parallel (takes up to 30 seconds).
- Review the performance scores and individual metric values. Fix Poor (red) metrics first, then Needs Improvement (amber) ones.
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FAQ
What are Core Web Vitals and why do they affect Google rankings?
Core Web Vitals are three specific performance metrics Google uses as part of its Page Experience ranking signal: LCP (loading), CLS (visual stability), and INP (interactivity). Google announced in 2021 that pages meeting the Good thresholds for all three get a ranking boost relative to pages that don't. They are the part of Google's algorithm you can directly measure and fix.
What is a good Core Web Vitals score?
Google defines 'Good' as: LCP under 2.5 seconds, CLS under 0.10, and INP under 200 milliseconds. 'Needs Improvement' is LCP 2.5–4 s, CLS 0.10–0.25, INP 200–500 ms. 'Poor' is anything above those ranges. The performance score (0–100) combines all metrics — 90+ is Good, 50–89 Needs Improvement, below 50 is Poor.
What is LCP and how do I improve it?
LCP (Largest Contentful Paint) measures how long it takes for the biggest visible element — usually a hero image or headline — to fully render. To improve LCP: use a CDN so content is served from servers close to the user, preload the hero image with <link rel='preload'>, compress and serve images in WebP or AVIF format, and eliminate render-blocking scripts in the <head>. Most LCP problems are image-related.
What is CLS and what causes layout shifts?
CLS (Cumulative Layout Shift) measures how much the page layout unexpectedly moves while loading — a score of 0 means perfectly stable. Common causes: images without explicit width and height attributes (browser doesn't reserve space until the image loads), ads injected above content, web fonts causing text to reflow (FOIT/FOUT), and dynamically injected banners or cookie notices. Fix by always declaring image dimensions and using font-display: optional or swap.
What is INP and how is it different from FID?
INP (Interaction to Next Paint) replaced FID (First Input Delay) as a Core Web Vitals metric in March 2024. FID only measured the delay before the browser started processing the first interaction. INP measures the full duration of all interactions — from the moment you click, tap, or press a key until the next frame is painted. A high INP means the page feels sluggish and unresponsive. Fix by reducing JavaScript execution time, breaking up long tasks, and avoiding layout-triggering JavaScript in event handlers.
Why does mobile score lower than desktop?
Google PageSpeed simulates mobile on a mid-range Android device with a throttled 4G connection — much slower than a typical desktop. Most pages score 10–30 points lower on mobile than desktop for this reason. Google's ranking primarily uses mobile scores because it uses mobile-first indexing, meaning the mobile version of your page is what determines your ranking.
How often should I check Core Web Vitals?
Check after every significant deployment — especially changes to images, fonts, JavaScript bundles, or third-party scripts. Also check after adding new features, A/B testing tools, chat widgets, or ad networks, as these commonly degrade CWV scores. Monthly checks are a good baseline for stable sites.
Is this the same as Google Search Console's Core Web Vitals report?
No — they measure differently. This tool uses lab data: a controlled simulation run by Google's Lighthouse engine at a fixed network speed. Google Search Console shows field data: real measurements from actual Chrome users visiting your page over 28 days. Lab data is useful for debugging specific pages instantly; field data reflects real-world user experience. Both matter — a page must pass field data thresholds to get the ranking boost.