Website speed is your website’s time to load in the browser.
Google uses data from the Chrome User Experience Report to measure performance data about the website. Certain Chrome users allow users to report back load time metrics to Google, with a current dataset enjoyed by Google already covering the top 1 million origins.
In early 2018, John Mueller at SMX confirmed that the PageSpeed Insights tool now includes the Chrome User Experience report data.
Recently, however, Google has been promoting Lighthouse, an open-source, automated tool for improving the quality of web pages. The PageSpeed Insights tool now uses Lighthouse to assess page speed.
You can access Lighthouse in Chrome by pressing F12 and then going to the “Audits” tab and running an audit. Alternatively, a new website has been launched, allowing you to run Lighthouse within the browser. You can find the new site at web.dev.
The Lighthouse will assess your mobile page speed based on smartphones and 3G internet. The CPU further throttles the page load, so using a lot of JavaScript could affect the load time.