This runs the real Lighthouse engine
Unlike a simple weight-and-timing proxy, this calls Google's actual PageSpeed Insights API - the same Lighthouse engine behind Chrome DevTools and Google's own PageSpeed Insights website - and returns genuine Performance, Accessibility, Best Practices, and SEO scores along with the specific opportunities Lighthouse flags for improvement.
Results are cached for 10 minutes per URL and device type to keep the tool responsive under load, since a full audit against Google's service takes real time to run.
Why mobile and desktop are checked separately
Lighthouse simulates genuinely different conditions for each strategy - a throttled mid-range mobile device and network connection for mobile, versus an unthrottled desktop environment for desktop - because real-world mobile visitors experience meaningfully worse conditions than desktop visitors, and Google's own ranking systems weigh mobile performance heavily given how much web traffic now happens on phones.
Why this differs from this site's other performance tools
This runs Google's own full Lighthouse audit covering four separate categories (Performance, Accessibility, Best Practices, SEO) with specific improvement opportunities - a different, more comprehensive scope than a simpler page-weight or load-time check, which measures a narrower set of raw technical metrics without Lighthouse's broader category scoring.
Why opportunities are listed, not just scores
A bare numeric score tells you how a page is doing, but not what to actually fix - Lighthouse's "opportunities" section identifies specific, actionable issues contributing to the score (like unoptimized images or render-blocking resources), which is generally more useful for actually improving a page than a number alone.