LCP
Largest Contentful Paint measures when the main content becomes visible. Aim for 2.5 seconds or less.
LonaDev · Free SEO utilities
Website Speed Test
Measure browser performance timings and resource transfer information for the page currently running this tool. For field data and full Core Web Vitals, use PageSpeed Insights or Chrome Lighthouse.
Free to useNo account requiredMobile friendlyInstant results
Run a browser timing test
This reads Navigation Timing and Resource Timing entries for the current document. It does not remotely benchmark a URL you type in, and results vary with device, network, cache and page state.
Test a website with field and lab data
For a full URL-based Lighthouse audit, enter your page in Google's PageSpeed Insights. It reports lab diagnostics and, when available, Chrome UX Report field data.
Open Google PageSpeed Insights ↗Understand Core Web Vitals
INP
Interaction to Next Paint measures responsiveness to user interactions. Aim for 200 milliseconds or less.
CLS
Cumulative Layout Shift measures unexpected visual movement. Aim for a score of 0.1 or less.
More free website tools
How this website speed test works
Measure browser timing data for this page and learn how to test LCP, INP and CLS with trusted field and lab tools.
Frequently asked questions
Does this test any URL I enter?
No. Browser security limits cross-origin performance access. This tool reads timing entries for the page where it runs. Use PageSpeed Insights or Lighthouse to test another URL.
What are Core Web Vitals?
They are Google web performance metrics focused on loading, responsiveness and visual stability: LCP, INP and CLS.