Core Web Vitals Checker
See how real visitors experience a page. Enter a URL or domain to get the Chrome UX Report field data Google uses for its Core Web Vitals assessment: Largest Contentful Paint, Interaction to Next Paint and Cumulative Layout Shift at the 75th percentile, for the page and the whole site, on mobile and desktop.
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How to use the Core Web Vitals Checker
- Enter the page URL or just a domain such as example.com.
- Choose the device: mobile and desktop together, or only one.
- Press Check Core Web Vitals and wait 10 to 60 seconds while Google answers.
- Read the verdict for the page and for the whole origin, then look at which metric is not green.
- Fix and re-check later: field data is a 28-day rolling average, so improvements show up gradually.
Core Web Vitals thresholds
| Metric | Measures | Good | Needs improvement | Poor |
|---|---|---|---|---|
| LCP Largest Contentful Paint | Loading of the main content | ≤ 2.5 s | 2.5 to 4.0 s | > 4.0 s |
| INP Interaction to Next Paint | Responsiveness to input | ≤ 200 ms | 200 to 500 ms | > 500 ms |
| CLS Cumulative Layout Shift | Visual stability | ≤ 0.1 | 0.1 to 0.25 | > 0.25 |
| FCP First Contentful Paint | First content on screen (supporting metric) | ≤ 1.8 s | 1.8 to 3.0 s | > 3.0 s |
| TTFB Time to First Byte | Server response (supporting metric) | ≤ 0.8 s | 0.8 to 1.8 s | > 1.8 s |
Values are the 75th percentile: three out of four visits were at least this fast. Mobile and desktop are assessed separately.
How to fix each Core Web Vital
Slow LCP
- Make the LCP image small and modern (WebP or AVIF, correct dimensions) and do not lazy-load it; add
fetchpriority="high". - Cut server response time with caching or a CDN; a slow TTFB delays everything after it.
- Remove render-blocking CSS and JavaScript from the
<head>, and preload the main web font.
Slow INP
- Break long JavaScript tasks into smaller pieces so the browser can respond between them.
- Remove or delay heavy third-party scripts (chat widgets, tag managers, A/B testing) that run on every click.
- Give instant visual feedback first, then do the expensive work; avoid re-rendering large parts of the page on each input.
High CLS
- Set
widthandheight(oraspect-ratio) on images, videos and iframes. - Reserve space for ads, embeds and banners before they load.
- Use
font-display: optionalor matched fallback fonts to prevent text jumping when web fonts load.
Use the Website Speed Test for a lab run with the specific files and elements behind each problem, and the Image Compressor to shrink a heavy LCP image.
Frequently asked questions
What are the Core Web Vitals thresholds?
Largest Contentful Paint (LCP) is good at 2.5 seconds or less and poor above 4 seconds. Interaction to Next Paint (INP) is good at 200 milliseconds or less and poor above 500 ms. Cumulative Layout Shift (CLS) is good at 0.1 or less and poor above 0.25. Each is measured at the 75th percentile of page loads.
How does Google decide if a page passes Core Web Vitals?
A page or site passes when the 75th percentile of LCP, INP and CLS are all in the good range, using data from real Chrome users over the previous 28 days. If INP has too few recorded interactions, the assessment is based on the metrics that have enough data.
What is the difference between field data and lab data?
Field data comes from real visitors on their own devices and networks, collected by Chrome in the Chrome UX Report. Lab data, such as a Lighthouse score, comes from one simulated load in a controlled environment. Google uses field data for its page experience signals; lab data is for debugging.
Why is there no data for my page?
The Chrome UX Report only includes pages and origins with enough eligible visits from Chrome users who share usage statistics. New, low-traffic or private pages often have no page-level data; the whole-origin data or a lab test is then the best guide.
Why did INP replace FID?
Interaction to Next Paint became a Core Web Vital in March 2024, replacing First Input Delay. FID only measured the delay before the first interaction was handled; INP looks at the responsiveness of all clicks, taps and key presses during a visit, so it reflects real sluggishness much better.
How long until my fixes show up?
The field data is a rolling 28-day window, so a fix starts to move the numbers within days and is fully reflected after about four weeks. Use lab tools such as the Website Speed Test to confirm the fix immediately.
Does this tool use an API key or store my URLs?
It calls Google's public PageSpeed Insights API directly from your browser without a key. The list of recent checks is saved only in your own browser. Because the free API is shared, it can be temporarily rate-limited when many people test at once.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.