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Free Core Web Vitals Checker

Run a Core Web Vitals check online and see what real Chrome users experienced on your site: 75th-percentile LCP, INP and CLS from the Chrome UX Report, mobile and desktop side by side. This is the same field data Google’s ranking systems read, so treat it as a fast CWV audit — it tells you whether your pages pass today, and which metric is costing you the most.

Field data vs lab data — which one is this?

This tool shows field data: measurements collected from real Chrome users who visited the site over the last 28 days, aggregated in Google's Chrome UX Report (CrUX). This is the same dataset Google's ranking systems read, which makes it the ground truth for "does Google think my site is fast?". It is different from lab data — what you get from a Lighthouse run — where one synthetic browser loads the page on a simulated connection. Lab data is reproducible and ideal for debugging a specific regression; field data is what your actual audience experienced, including their slow phones, flaky trains and distant geographies. You need both: field data to know whether you have a problem, lab data to find and fix it.

What the numbers mean

Every metric is reported at the 75th percentile — three quarters of visits were at least this fast. LCP (Largest Contentful Paint, good ≤ 2.5 s) is how long the main content took to appear. INP (Interaction to Next Paint, good ≤ 200 ms) is how quickly the page responds when users tap and type — it replaced FID in 2024. CLS(Cumulative Layout Shift, good ≤ 0.1) measures how much the layout jumps around while loading. The tool also shows FCP and TTFB, which are diagnostic: a slow TTFB (> 800 ms) usually means server or CDN problems and drags every other metric down with it. The colored bar under each metric is the distribution of real visits across good / needs-improvement / poor.

How to fix poor vitals

Poor LCP: compress and preload the hero image, serve it in WebP/AVIF, cut server response time with caching or a CDN, and remove render-blocking scripts. Poor INP: break up long JavaScript tasks, defer third-party tags (chat widgets and analytics are the usual offenders), and avoid re-rendering huge component trees on input. Poor CLS: give images and embeds explicit width/height, reserve space for ads and banners, and never inject content above existing content after load. If the checker reports origin-level data only, your individual page lacks traffic — the whole-site aggregate still tells you where you stand.

Frequently asked questions

What is the difference between field data and lab data?

Field data is measured on real visitors’ devices and aggregated by Chrome (CrUX) — it is what Google actually uses for ranking. Lab data comes from a controlled test run (like Lighthouse) — perfectly reproducible and great for debugging, but it reflects one synthetic device and network, not your audience.

Why does my site show "no field data"?

CrUX only publishes data for origins and URLs with enough Chrome traffic — roughly a few thousand eligible visits per month. Smaller sites, new pages, intranets and sites with mostly Safari/Firefox audiences will not appear. Use a lab test to measure and optimize until you have field data.

What are good Core Web Vitals scores?

At the 75th percentile: LCP ≤ 2.5 s, INP ≤ 200 ms, and CLS ≤ 0.1. Google rates each metric good / needs improvement / poor, and a page passes the assessment only when all three core metrics are good.

Do Core Web Vitals affect rankings?

Yes, as part of the page experience signals — a tiebreaker rather than a dominant factor. In practice the indirect effects are bigger: slow LCP and janky CLS raise bounce rates, and bounce kills conversions regardless of rank.

Why do mobile and desktop numbers differ so much?

Mobile users are on slower CPUs and radio networks, so LCP and INP are almost always worse there. Google indexes and evaluates mobile-first, so fix the mobile column first.

Want the full picture?

This tool checks one thing. A full RankVitals audit runs a Lighthouse speed test plus 50+ SEO and AI-readiness checks on your whole site — free, no signup.

Run a full site audit →