Core Web Vitals Checker
Measure your site's Core Web Vitals — LCP, INP, and CLS — the metrics Google uses to rank your pages. Get lab data, real-world CrUX data, and actionable fixes.
What Are Core Web Vitals?
Core Web Vitals are a set of real-world, user-centered metrics that Google uses as ranking signals. They measure loading performance, interactivity, and visual stability of your pages.
Largest Contentful Paint (LCP)
Measures loading performance — how long it takes for the largest visible element (image, heading, or block of text) to render. Aim for under 2.5 seconds. Common causes of slow LCP include unoptimized images, slow server response, render-blocking resources, and client-side rendering delays.
Interaction to Next Paint (INP)
Measures responsiveness — how long the page takes to respond to user interactions (clicks, taps, key presses). Aim for under 200 milliseconds. INP replaced First Input Delay (FID) as a Core Web Vital in March 2024. Improve INP by reducing JavaScript execution time and breaking up long tasks.
Cumulative Layout Shift (CLS)
Measures visual stability — how much the page layout shifts unexpectedly during loading. Aim for under 0.1. CLS is caused by images/ads without dimensions, dynamically injected content, web fonts that cause FOIT/FOUT, and late-loading third-party embeds.
Lab Data vs. Field Data
This tool shows both lab data (simulated Lighthouse tests) and field data (real Chrome user measurements from CrUX). Field data is what Google actually uses for ranking, but it requires your site to have enough traffic. Lab data is always available and useful for diagnosing issues.
Performance Score Breakdown:
- A (90-100) - Excellent performance
- B (70-89) - Good, minor optimizations
- C (50-69) - Fair, needs improvement
- D (30-49) - Poor, needs attention
- F (0-29) - Critical issues detected
Need Help Improving Your Core Web Vitals?
Our team can optimize your LCP, INP, and CLS scores to improve Google rankings and user experience. We handle image optimization, code splitting, layout stability, and more.