Google Lighthouse

What is Google Lighthouse?

Google Lighthouse is an open-source tool that audits a web page and reports on five areas: performance, accessibility, best practices, SEO, and progressive web app readiness. It loads the page in a controlled environment, measures dozens of signals, and returns a score from 0 to 100 for each category alongside specific things to fix.

Google released it in 2016, and it now ships inside Chrome DevTools, runs from the command line, and powers PageSpeed Insights. Its performance score is built on Core Web Vitals, the metrics Google uses in search ranking, which is why the tool sits at the center of so many optimization efforts. Largest Contentful Paint, Cumulative Layout Shift, and Total Blocking Time each feed the number. A team watching their mobile performance score sit at 45 will use Lighthouse to find the render-blocking scripts and oversized images dragging it down. One caveat worth holding onto: a lab score is a snapshot under fixed conditions, not a guarantee of what every real user experiences.

The scores are a starting point for a conversation, not a grade to chase blindly. A page can score 100 and still feel slow on a cheap phone in a weak signal, which is exactly why the tool reports field data too.

Google Lighthouse at Dallonses

We run Lighthouse as part of the pipeline, not as a one-off check before launch. Wiring performance audits into CI/CD means a regression shows up in a pull request, while it is cheap to fix, instead of in production a month later. A budget that fails the build keeps performance honest as a site grows.

We treat the score as a tool, not a trophy. When a partner asks us to make a site faster, we use Lighthouse to find the real bottlenecks and then verify the fix against actual devices and connections. The goal is a site that feels fast to the person using it, and the number is how we keep track.

Site scoring lower than it should? Let's find what's slowing it down.

Talk to us about performance