Google PageSpeed Insights
Google PageSpeed Insights (PSI) analyses the content of a web page, then generates suggestions to make that page faster.
PSI provides a score which summarizes the page's performance. This score is determined by running Lighthouse to collect and analyze lab data about the page. A score of 90 or above is considered good. 50 to 90 is a score that needs improvement, and below 50 is considered poor.
Google already uses page speed in their ranking algorithm, and plan to incorporate Page Experience in their ranking algorithm as well, through the Web Vitals initiative.
Test your web pages with the free Google PageSpeed Insights Tool, you don't need to sign up or register to use it.