Free tool
Core Web Vitals Checker
Run the core web vitals checker
Free, no sign-up. You get the full LaunchSafer report, including the checks below, in 30–90 seconds.
The three Core Web Vitals
Largest Contentful Paint (LCP) measures loading: aim for 2.5 seconds or less. Cumulative Layout Shift (CLS) measures visual stability: aim for 0.1 or less. Interaction to Next Paint (INP) measures responsiveness: aim for 200 ms or less.
INP can only come from real visitors. If Google hasn't collected enough real-user data for your site, LaunchSafer marks INP as not tested and shows Total Blocking Time, its closest lab equivalent.
Lab data vs field data
Lab data comes from a single Lighthouse run on a simulated device, so it's repeatable but can differ from real life. Field data is the 75th percentile of real Chrome users over 28 days. The report labels the two separately and never mixes them.
Frequently asked questions
Where does the data come from?
Google PageSpeed Insights: Lighthouse lab measurements plus Chrome UX Report field data when available.
Why is INP marked not tested?
INP needs real visitors' interactions. Google only reports it for sites with enough Chrome traffic.
Do Core Web Vitals affect SEO?
They are part of Google's page experience signals. Relevance matters more, but slow pages also lose visitors.