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Term

Lighthouse

Lighthouse is Google's open-source audit tool that synthetically measures a page's performance, accessibility, best practices, and SEO in a controlled environment.

Lighthouse — explained in more detail

Lighthouse runs directly inside Chrome DevTools, as a CLI, or in CI pipelines and performs a simulated measurement against a URL. The five categories (Performance, Accessibility, Best Practices, SEO, Progressive Web App) each yield a 0–100 score plus concrete optimization suggestions — for example “Serve images in next-gen formats” or “Reduce render-blocking JavaScript”.

Lighthouse simulates a standardized environment (throttled CPU, throttled network) so measurements stay reproducible. That’s both its strength and its weakness: great for A/B comparisons during optimization, but not a picture of real user experience.

Example / practical use

Before a deploy, you can run Lighthouse via the CLI against staging and link the score as a pull request check — performance regressions show up before the merge.

Lighthouse delivers lab data (synthetic, one device, one run). For rankings, however, Google evaluates field data from the CrUX report (real Chrome users). PageSpeed Insights combines both — Lighthouse scores plus CrUX field data in a single interface.

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