PageSpeed Insights and Lighthouse use the same engine, but they run in different places. PageSpeed Insights runs Lighthouse on Google’s servers and adds real-user data from Chrome, while Lighthouse in Chrome DevTools runs on your own computer. That is why their scores can differ for the same page. Compare both with our free website speed test.
Key takeaways
- PageSpeed Insights is a web tool that runs Lighthouse for you and adds field data from real users.
- Lighthouse is the testing engine. You can run it in Chrome DevTools or from the command line.
- Lighthouse in DevTools can test pages that are not public, such as a staging site.
- Use PageSpeed Insights for a quick Google view and Lighthouse for debugging.
What is Lighthouse?
Lighthouse is an open-source tool from Google that audits a page for performance, accessibility, best practices and SEO. It produces a score for each category and a list of issues. You can run it in Chrome DevTools, from the command line or as part of a build process.
What is PageSpeed Insights?
PageSpeed Insights is a free Google web tool that tests a public URL on mobile and desktop. It runs Lighthouse on Google’s servers and adds field data from real Chrome users when enough data exists. For a walkthrough, see how to use Google PageSpeed Insights.
What is the difference between PageSpeed Insights and Lighthouse?
| Feature | PageSpeed Insights | Lighthouse (DevTools) |
|---|---|---|
| Where it runs | Google’s servers | Your own computer |
| Field data | Yes, when enough data exists | No |
| Pages it can test | Public URLs | Public and non-public pages |
| Results depend on | Google’s test setup | Your device, connection and extensions |
| Best for | Quick check and Core Web Vitals | Debugging and pre-launch testing |
Why do the scores differ?
The scores differ because the tests run on different hardware and networks. Lighthouse in DevTools uses your computer and connection, so a fast laptop or an installed browser extension can change the result. PageSpeed Insights uses a standard setup on Google’s servers. Small differences are normal. Read more in our guide on PageSpeed Insights accuracy.
When should you use Lighthouse?
- Testing a page before you publish it.
- Testing a staging site or a page behind a login.
- Debugging a specific issue with the Performance panel.
- Running repeated tests as part of a development process.
To get cleaner results, test in an incognito window with extensions turned off.
When should you use PageSpeed Insights?
- Checking how real visitors experience a live page.
- Checking Core Web Vitals. See our Core Web Vitals test guide.
- Getting a quick score on mobile and desktop.
How do you improve your score in either tool?
The fixes are the same in both: compress images, enable caching, remove unused JavaScript and reduce render-blocking files. Follow our guide on how to improve website speed, then re-test. Score ranges are explained in what a good PageSpeed score is.
Frequently asked questions
Is Lighthouse the same as PageSpeed Insights?
No. Lighthouse is the testing engine, and PageSpeed Insights is a web tool that runs it and adds real-user data.
Which is more accurate?
Neither is more accurate. They test under different conditions, so use one consistently and compare results over time.
Can Lighthouse show Core Web Vitals from real users?
No. Lighthouse gives lab results only. Real-user data comes from PageSpeed Insights and the Search Console report.
Do both tools give the same fix suggestions?
Mostly yes, because they use the same audits. Results can differ slightly if the test conditions differ.
Is Lighthouse free?
Yes. It is free and built into Chrome DevTools.
Conclusion
PageSpeed Insights gives you Google’s view with real-user data, and Lighthouse gives you a flexible local test. Use both: PageSpeed Insights to check, Lighthouse to debug. Cross-check with our free website speed test.
