Lighthouse is an open-source automated auditing tool built by Google that analyzes a web page and produces scores and diagnostic recommendations across five categories: Performance, Accessibility, Best Practices, SEO, and Progressive Web App (PWA) readiness. Each category produces a 0–100 score; a Performance score above 90 is considered good. The Performance score is a weighted composite of Core Web Vitals and related metrics including Total Blocking Time, Speed Index, and Time to Interactive. Lighthouse runs in Chrome DevTools (under the Lighthouse tab in the developer panel), in Google PageSpeed Insights, and as a Node.js CLI or npm package for CI/CD integration. Because Lighthouse simulates a throttled mid-range mobile device connection by default, its scores reflect lab conditions rather than real-user field data — CrUX (Chrome User Experience Report) provides the field data that actually informs Core Web Vitals ranking signals. Lighthouse is best used for diagnosing specific performance issues; field data from PageSpeed Insights or Search Console confirms real-world impact.
Glossary entry
