What the report shows
Each test runs Google's Lighthouse engine on a simulated mobile phone or desktop computer and, when Google has enough Chrome traffic data, adds real-user Core Web Vitals from the Chrome UX Report.
| Section | What it tells you |
|---|---|
| Four scores | Performance, Accessibility, Best Practices and SEO, each from 0 to 100 |
| Real-user Core Web Vitals | LCP, INP and CLS measured on real Chrome visitors over the last 28 days, with a pass or fail assessment |
| Lab metrics | First Contentful Paint, Largest Contentful Paint, Total Blocking Time, Cumulative Layout Shift and Speed Index from the simulated test |
| Filmstrip and screenshot | How the page looks at each moment while it loads |
| Audits to review | Opportunities ranked by estimated time saved, plus failing accessibility, best-practice and SEO checks |
How to read the scores
Scores of 90–100 are good (green), 50–89 need improvement (orange) and 0–49 are poor (red). The Performance score is a weighted mix of the lab metrics, so it can change by a few points between runs as network conditions vary. Test two or three times and compare the median.
Core Web Vitals thresholds
| Metric | Good | Poor |
|---|---|---|
| Largest Contentful Paint (LCP) | ≤ 2.5 s | > 4 s |
| Interaction to Next Paint (INP) | ≤ 200 ms | > 500 ms |
| Cumulative Layout Shift (CLS) | ≤ 0.1 | > 0.25 |
The fixes that help most
- Optimise the largest image — serve it as WebP or AVIF at the size it is displayed, and do not lazy-load it.
- Remove render-blocking resources — inline critical CSS and defer scripts that are not needed for the first view.
- Cut unused JavaScript and third-party tags; they are the main cause of a high Total Blocking Time.
- Reserve space for images, ads and embeds with width and height attributes so the layout does not shift.
- Speed up the server — caching, compression and a CDN lower Time to First Byte. Check the raw HTML weight with the Page Size Checker.
For on-page factors that Lighthouse does not cover, such as titles, headings and structured data, run the SEO Audit.
Frequently asked questions
Is this website speed test free?
Yes. It is free with no sign-up. Each test takes about 15 to 60 seconds because Google loads the page in a real browser.
Is this the same as Google PageSpeed Insights?
Yes. The test uses the official Google PageSpeed Insights API, so the scores and audits come from the same Lighthouse engine as pagespeed.web.dev.
Why is my mobile score lower than desktop?
The mobile test simulates a mid-range phone on a slow 4G connection, so CPU-heavy pages and large images score lower than on the desktop test.
Why does the score change between tests?
Lab scores vary by a few points because network and server response times differ on each run. Run the test several times and use the typical result.
What if there is no real-user data?
Real-user Core Web Vitals appear only when the page or site has enough Chrome visitors. New or low-traffic sites show lab results only.