Core Web Vitals checker: understand LCP, CLS and INP.
Core Web Vitals are the user-experience metrics Google uses as a ranking signal. WebCheck tests them on your page and explains what each result means and how to improve it.
The three Core Web Vitals
- Largest Contentful Paint (LCP): how long the main content takes to appear. Good: 2.5 seconds or less.
- Interaction to Next Paint (INP): how quickly the page reacts to clicks and typing. Good: 200 milliseconds or less.
- Cumulative Layout Shift (CLS): how much the page moves while loading. Good: 0.1 or less.
Lab data and field data
WebCheck runs a lab test: a controlled simulation that is ideal for finding causes and checking fixes. Google’s ranking signal uses field data collected from real Chrome users over 28 days. INP needs real interactions, so in a lab test it is approximated by Total Blocking Time.
Use WebCheck to diagnose and fix, then watch the Core Web Vitals report in Google Search Console to confirm the improvement for real visitors.
How to improve each Core Web Vital
- LCP: compress and resize the main image, preload it, reduce server response time and remove render-blocking files.
- INP: split long JavaScript tasks, defer non-essential scripts and limit third-party code.
- CLS: set width and height on images and embeds, reserve space for ads and avoid late font swaps.
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Run a free auditFrequently asked questions
Do Core Web Vitals affect SEO?
They are part of Google’s page experience signals. They rarely outweigh relevant content, but they can make the difference between similar pages and they directly affect visitors.
Why do my lab results differ from Search Console?
Search Console shows real-user data from the last 28 days, across many devices and networks. Lab tests show one controlled run. Both are useful for different purposes.
How often should I check Core Web Vitals?
After every significant change to a page (new theme, plugin, images or scripts) and once a month for your key pages.
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Updated 22 October 2026