PageSpeed Insights (PSI) is a free tool from Google that analyzes the performance of web pages on both mobile and desktop devices. It provides both lab data (from Lighthouse) and field data (from the Chrome User Experience Report).
What PSI provides
- Field Data: Real-world Core Web Vitals from actual Chrome users
- Lab Data: Lighthouse performance audit results
- Opportunities: Suggestions for improving performance
- Diagnostics: More detailed information about best practices
PSI scores
PSI shows both field data metrics and a Lighthouse performance score:
- 0-49: Poor (red)
- 50-89: Needs Improvement (orange)
- 90-100: Good (green)
Field vs Lab data
- Field data: From real Chrome users over the past 28 days
- Lab data: From a single Lighthouse run in a controlled environment
Field data is more representative of actual user experience, while lab data is useful for debugging specific issues.
How VitalSentinel handles this
PSI is great for spot checks, but it does not run on a schedule or alert you to regressions. VitalSentinel's Synthetic Monitoring runs Lighthouse audits continuously on your key URLs, stores the history, and notifies you the moment scores drop so you can fix issues in hours instead of finding out from a Slack screenshot.
Related Terms
Chrome User Experience Report (CrUX)
A public dataset of real user experience data from millions of websites, collected from Chrome users who have opted in to usage statistic reporting.
Core Web Vitals
A set of three metrics defined by Google that measure the loading performance, interactivity, and visual stability of a web page.
Lab Data
Performance metrics collected in controlled testing environments using tools like Lighthouse, as opposed to field data from real users.
Lighthouse
An open-source automated tool by Google for auditing the quality of web pages, measuring performance, accessibility, SEO, and more.