Google PageSpeed Insights

PageSpeed Insights (PSI) measures the performance of a page on both mobile and desktop devices and then provides suggestions to improve that page.

PageSpeed Insights is powered by Lighthouse since the end of 2018. This means that the results in your PSI reports are based on the Lighthouse API.

When scanning a page, PageSpeed provides two types of data: Lab and Field data.

Lab data is collected in a controlled environment with a set of predefined devices and network settings. It effectively debugs performance issues, and its testing can be easily reproduced. However, it might fail in catching real-world bottlenecks.

On the other hand, field data (also called Real User Monitoring or RUM) includes performance data coming from real page loads. It’s effective to capture true, real-world user experience, but the set of metrics and its debugging potential is limited.