Glossary · SEO & Search
Lighthouse
Overview
What Lighthouse is
Lighthouse is an open-source tool from Google that audits the quality of a web page. It runs a series of tests against a URL and returns scores, from 0 to 100, in categories including Performance, Accessibility, Best Practices, and SEO. You can run it in Chrome DevTools, from the command line, as a Node module, or through PageSpeed Insights.
What it measures
The Performance score is built largely from lab measurements of Core Web Vitals and related metrics like Largest Contentful Paint and Total Blocking Time. Other categories check for accessibility problems, insecure or outdated practices, and basic on-page SEO signals. Crucially, each audit lists concrete opportunities, such as deferring a script or compressing an image, not just a grade.
How we use Lighthouse
Our frontend development and technical SEO teams run Lighthouse throughout website redesign and build work to catch regressions before launch. Because its performance scoring maps to Core Web Vitals, it helps us tune real user experience, not just a number. We treat lab scores as a guide and confirm outcomes with field data from Google Search Console.
Where we use it
Related Zen in Tech services
How our team puts Lighthouse to work in real projects.
FAQ
Lighthouse — common questions
Is a good Lighthouse score the same as ranking well?
Not directly. Lighthouse measures page quality signals, including Core Web Vitals, which are a ranking factor, but a high score does not guarantee rankings. Content relevance, links, and overall SEO still determine where a page ranks.
What is a good Lighthouse performance score?
Google labels 90 to 100 as good (green), 50 to 89 as needs improvement, and 0 to 49 as poor. Scores vary between runs due to network and device conditions, so look at trends and field data, not a single result.
Lighthouse vs PageSpeed Insights?
They use the same Lighthouse engine. PageSpeed Insights runs it on Google's servers and adds real-world field data (CrUX), while the Chrome DevTools version runs a lab test on your own machine.
Keep exploring
Related terms
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