The Page Speed Checker runs Google's PageSpeed test on a page for mobile and gives a score out of 100. You also get Largest Contentful Paint, Cumulative Layout Shift, Total Blocking Time and Speed Index, plus a list of the biggest issues with their impact. If Google's test does not respond, it measures the page's HTML itself and says so.
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The headline is the mobile score out of 100. 90 and above passes, 50 to 89 is a warning and below 50 fails.
These are lab numbers from Google Lighthouse on mobile. Real-user numbers can differ.
| Metric | Target | What it covers |
|---|---|---|
| Largest Contentful Paint | Under 2.5s | How long the biggest element takes to appear |
| Cumulative Layout Shift | Under 0.1 | How much the page jumps around while loading |
| Total Blocking Time | Under 200ms | How long scripts keep the page from responding |
| Speed Index | No target shown | How quickly the visible part fills in |
The tool then measures the page itself, and the summary says so. It reports the time to fetch the HTML, the HTML size, render-blocking scripts in the head, the number of stylesheets in the head and how many images use lazy loading. These are not Core Web Vitals.
HTML arrives quickly passes at 800ms or less. HTML is not oversized passes at 150KB or less. Nothing blocks the first paint passes with no blocking scripts. Few stylesheets in the head passes at 3 or fewer. The fetch runs from a server on a fast connection, so real visitors on mobile will see slower times.
The "What is costing you" table lists up to 8 issues from Google with the potential saving. Start at the top.
Peak Answer runs checks like these every week, then writes the content and gets the placements.