Google Pagespeed Insight
Google Pagespeed Insight - 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 about it: Lab and Field data. - Lab data is collected in a controlled environment, that is with a set of predefined devices and network settings. It is effective for debugging 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 is limited as well as its debugging potential.