Google Lighthouse — site scoring in 5 areas: Performance, Accessibility, Best Practices, SEO, PWA.
Run
Chrome DevTools → Lighthouse → Generate.
Performance
0-100. 90+ green. FCP, LCP, TBT, CLS.
CLI
npm i -g lighthouse — automate in CI/CD.
Top fixes
WebP, defer CSS/JS, reduce unused CSS, image sizing, gzip/brotli.