Google Lighthouse is a free, open-source tool from Google that runs automated audits on any web page and scores it across performance, accessibility, best practices, and SEO. It flags specific problems, explains their impact, and suggests fixes, giving teams a repeatable benchmark they can track over time.
Each category returns a score from 0 to 100. The performance score gets the most attention because it is built from Core Web Vitals: Largest Contentful Paint (LCP), Interaction to Next Paint (INP, which replaced First Input Delay in 2024), and Cumulative Layout Shift (CLS). These metrics are weighted, so one slow hero image or a jumpy layout can pull the whole number down.
Worth knowing: the SEO category is a lightweight technical check of roughly a dozen items, such as whether the page is crawlable, has a title and meta description, and uses legible font sizes. Passing it is a baseline, not proof that your content will rank.
A furniture retailer's product page scored 38 on mobile performance. Lighthouse traced an LCP of 5.8 seconds to a 1.4 MB uncompressed hero image plus three render-blocking scripts. After the team served the image as WebP at 180 KB, deferred the scripts, and lazy-loaded below-the-fold photos, LCP fell to 2.1 seconds and the score climbed to 84. The most common wins it surfaces:
Lighthouse produces lab data, a simulated test on a fixed device and connection, so a single run can swing a few points between tests. Real users may experience something different, which is why field data from the Chrome User Experience Report matters too. Treat Lighthouse as a diagnostic starting point within a broader technical SEO program, and pair its scores with real-world monitoring of your user experience. You can run it from Chrome DevTools, PageSpeed Insights, the command line, or inside a CI pipeline.