Lighthouse is Google's open-source automated auditing tool for web pages. It produces a 0-100 score across performance, accessibility, best practices, SEO, and PWA, plus actionable recommendations.
Lighthouse runs against a single URL using Chrome under simulated mobile conditions (Slow 4G throttle, mid-tier CPU). It is the engine behind PageSpeed Insights, Chrome DevTools' Audits panel, and many CI integrations.
Key distinction: Lighthouse is **lab data** — synthetic, repeatable, but not necessarily representative of real users. Lab and field (CrUX) numbers can disagree significantly. Both matter: lab catches regressions in CI, field tells you what users actually experience.
Lighthouse is the de-facto standard for web performance auditing. Building a Lighthouse run into your CI prevents performance regressions before deploy, and tracking the score over time reveals whether your team is investing in performance or trading it away.
See it in the product: Lighthouse audits.