Core Web Vitals Checker
The three metrics Google ranks on — LCP, INP and CLS — from real Chrome-user field data when available, plus the Lighthouse lab score, with a fix for whatever’s failing. Tested on mobile.
The three Core Web Vitals
- LCP — Largest Contentful Paint (loading): good ≤ 2.5s. When the main content appears.
- INP — Interaction to Next Paint (responsiveness): good ≤ 200ms. How quickly the page reacts to input. Replaced FID in 2024.
- CLS — Cumulative Layout Shift (visual stability): good ≤ 0.1. How much the layout jumps as it loads.
Field vs lab data
Field data is what real Chrome users experienced over the last 28 days (CrUX) — this is what Google actually ranks on. It only exists once a page/site has enough traffic; for quieter sites we show the lab result from a single Lighthouse run instead. INP is a field-only metric, so it may read as “no data” on low-traffic pages.
Related
- Website Speed Test (server timing / TTFB), HTTP Header Checker.
Frequently asked questions
▸ ▾ What are good Core Web Vitals?
LCP 2.5s or less, INP 200ms or less, and CLS 0.1 or less, measured at the 75th percentile of your real users.
▸ ▾ Why is there no field data for my site?
Field (CrUX) data only exists for pages with enough real Chrome traffic. Low-traffic sites fall back to lab (Lighthouse) data, and INP is field-only.