Run Lighthouse on any URL for mobile and desktop and get performance scores and Core Web Vitals.
How to use the PageSpeed checker
- Enter a URL.
- Wait for the mobile and desktop runs.
- Fix the biggest opportunities first, usually images and render-blocking scripts.
Core Web Vitals
LCP (how fast the main content shows, under 2.5 s), INP (how quickly the page responds to input, under 200 ms) and CLS (how much the layout jumps, under 0.1). Google uses real-user data for these as a ranking signal.
How to read the scores
The four circles are Lighthouse scores for performance, accessibility, best practices and SEO. 90–100 is good, 50–89 needs work and under 50 is poor. Lab metrics come from one simulated load and are coloured the same way: First Contentful Paint is good under 1.8 s, Largest Contentful Paint under 2.5 s, Total Blocking Time under 200 ms, Cumulative Layout Shift under 0.1, and Speed Index under 3.4 s on mobile. The real-users panel shows Chrome field data over 28 days at the 75th percentile; this is what Google uses. Poor field values start at LCP over 4 s, INP over 500 ms and CLS over 0.25. Mobile uses a slow phone and network, so it always scores lower than desktop.
Fixing the usual causes
Slow LCP: compress and resize the hero image, serve WebP or AVIF, don't lazy-load the image at the top of the page, and speed up the server response. High Total Blocking Time or poor INP: cut and defer JavaScript, especially third-party chat widgets, tag managers and A/B tools. Layout shift: give images and embeds width and height, reserve space for banners, and use font-display: swap with a similar fallback font. If there is no field data, the site doesn't get enough Chrome traffic yet; rely on lab numbers.