Core Web Vitals Checker
Check LCP, INP and CLS for any page, using real-user data from Google where it exists, and see which parts of the page are holding the numbers back.
Measuring the page. Google's lab test can take up to a minute.
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Core Web Vitals Checker - results and guide
What the Core Web Vitals Checker checks
- LCP, INP and CLS at the 75th percentile from the Chrome UX Report, when Google has data
- The pass or fail assessment Google applies
- A Lighthouse lab run with performance score, on mobile or desktop
- Server response time and text compression
- Render-blocking stylesheets and scripts in the head
- Images without dimensions and a lazy-loaded first image
- Amount of JavaScript, third-party script hosts and DOM size
What are Core Web Vitals?
Core Web Vitals are three measurements Google uses to describe how a page feels to a visitor. Largest Contentful Paint (LCP) is how long the main content takes to appear: good is 2.5 seconds or less. Interaction to Next Paint (INP) is how quickly the page reacts to a tap, click or key press: good is 200 milliseconds or less. Cumulative Layout Shift (CLS) is how much the layout jumps while loading: good is 0.1 or less.
A page passes when all three are good for at least 75% of visits. The figures come from real Chrome users over the previous 28 days, collected in the Chrome UX Report, and they are part of Google's page experience ranking signals.
Field data and lab data
Field data is what real visitors experienced on their own devices and networks. It is what Google uses, but it exists only for pages and sites with enough traffic. Lab data is a single simulated load in controlled conditions. It is available for any page and is the right tool for debugging, but its numbers will not match the field exactly. INP has no lab equivalent; Total Blocking Time is the closest stand-in.
This tool shows Google's data when it is available and always reviews the page itself for the usual causes: a slow server, render-blocking files, uncompressed text, images without dimensions and heavy JavaScript. Server response time is the one part of LCP that can change from hour to hour: Upmonora's website monitoring tracks it around the clock and flags slowdowns.
How to use the Core Web Vitals Checker
- Enter the address of the page you want to check. You can leave out
https://. - Choose whether to test as a phone or as a desktop computer.
- Press Check vitals. The page is fetched from our servers, the way a search engine crawler would fetch it.
- Read the findings from top to bottom: problems first, then warnings. Each one says what to change.
Common problems and how to fix them
LCP is slow
Cut server response time with caching or a CDN, compress and correctly size the hero image, preload it or mark it fetchpriority="high", and remove render-blocking CSS and JavaScript.
CLS is high
Add width and height to every image and video, reserve space for ads and embeds, and avoid inserting banners above content that is already visible.
INP is slow
Reduce and split long JavaScript tasks, load third-party scripts after the page is interactive, and keep event handlers light.
Frequently asked questions
What is a good Core Web Vitals score?
Are Core Web Vitals a ranking factor?
Why is there no field data for my page?
What replaced First Input Delay?
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