What we check
Performance: how quickly the page loads and becomes usable on a phone over a mobile connection, measured by Lighthouse. Search: the technical signals search engines read, such as titles, crawlability and structured data. Accessibility: automated checks for contrast, labels, alt text and keyboard use. Best practice: browser errors, outdated APIs and other quality signals.
Security: whether the page is served over HTTPS with the headers that protect visitors, such as HSTS and a Content Security Policy, and whether your server advertises its software versions.
Lab scores and real visitors
Lighthouse scores come from a single simulated visit, so they move a few points between runs. Where Google has enough data from real Chrome users of your page, we also show the Core Web Vitals those visitors experienced over the last 28 days. Those are the numbers Google uses as a ranking signal.
What an automated check cannot tell you
Automated accessibility tests catch roughly a third of real problems; the rest need a person with a keyboard and a screen reader. Security headers are only the surface; they say nothing about the code or server behind them. Use this as a quick health check, not a full audit.