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Core Web Vitals Checker
Check any site's real-user Core Web Vitals — LCP, INP, CLS from Google's Chrome UX Report field data, the same 28-day measurements Google assesses for rankings.
Quick answer
What are Core Web Vitals?
Core Web Vitals are Google's three field-measured user-experience metrics: Largest Contentful Paint (LCP — loading, good under 2.5s), Interaction to Next Paint (INP — responsiveness, good under 200ms), and Cumulative Layout Shift (CLS — visual stability, good under 0.1). Google assesses them from real Chrome users' visits, and they form the page-experience signal used in ranking.
Field data vs lab data — why this checker uses field data
Lab tools (like a Lighthouse run) simulate one synthetic visit from one machine. Field data is what real users actually experienced over the last 28 days — and it's what Google uses for the ranking signal. A page can score 95 in a lab run and still fail Core Web Vitals in the field on slow phones and networks.
This checker reads the official Chrome UX Report field data for your origin: the 75th-percentile value of each metric plus the share of real visits rated good, needs-improvement, and poor.
How to fix each metric
- LCP too slow: compress and preload the hero image, cut server response time (TTFB), and eliminate render-blocking scripts and stylesheets above the fold.
- INP too high: break up long JavaScript tasks, defer third-party scripts (chat widgets and tag managers are the usual culprits), and debounce expensive input handlers.
- CLS too high: set explicit width/height on images and embeds, reserve space for ads and banners, and never inject content above what the user is reading.
- TTFB dragging everything: add caching or a CDN in front of your origin — every metric downstream benefits.
Vitals, SEO, and AI search
Core Web Vitals are a real but modest ranking signal — content relevance still dominates. Their compounding value is behavioral: faster, stabler pages cut abandonment, raise conversion, and increase the dwell-and-return signals that correlate with durable rankings. Fast, cleanly-rendered pages are also easier for AI crawlers to fetch and parse within their time budgets.
Where this data comes from
All numbers come from the official Chrome UX Report (CrUX) API — Google's public dataset of real Chrome users' experiences, aggregated over a 28-day rolling window and refreshed daily. We show the p75 value Google uses for assessment plus the good/needs-improvement/poor distribution for LCP, INP, CLS, TTFB, and FCP, with the device split. Origins with too little real-user traffic have no CrUX data; we report that honestly rather than substituting a lab simulation.
Frequently asked questions
What are good Core Web Vitals scores?
Google's thresholds, assessed at the 75th percentile of real visits: LCP under 2.5 seconds, INP under 200 milliseconds, and CLS under 0.1. A page passes Core Web Vitals when all three core metrics are 'good' at p75 — meaning at least three-quarters of real visits had a good experience.
Why does my site show no Core Web Vitals data?
The Chrome UX Report only publishes data for origins with sufficient real Chrome traffic. Newer and lower-traffic sites often fall below that threshold. In that case, use lab testing (Lighthouse/PageSpeed Insights) to catch obvious issues, and re-check here as traffic grows.
Do Core Web Vitals affect Google rankings?
Yes, as part of the page-experience signal — but modestly. Google has been clear that great content outranks great vitals. Treat vitals as a tiebreaker in competitive results and a conversion lever everywhere: the revenue case for speed is usually stronger than the pure-ranking case.
What's the difference between this and PageSpeed Insights?
PageSpeed Insights combines a lab simulation with field data. This checker reports the field data alone — the real-user measurements Google actually assesses — which makes it the right tool for 'am I passing?' while lab tools remain right for 'what exactly do I fix?'
What is INP and why did it replace FID?
Interaction to Next Paint measures the latency of all user interactions on a page, not just the first input as FID did. Google made INP a Core Web Vital in March 2024 because it better captures sustained responsiveness — pages heavy on JavaScript that felt fine on first click but janky afterward now get measured accurately.
How often does this data update?
The CrUX API serves a 28-day rolling aggregate refreshed daily. After you ship a performance fix, expect the field numbers to converge on the new reality over roughly four weeks as old visits age out of the window.
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