Google's goal is to provide users with the most relevant results and a great user experience. Fast sites increase user satisfaction and improve the overall quality of the web (especially for those users with slow internet connections), and Google hopes that as webmasters improve their sites, the overall speed of the web will improve.

Site Performance is an experimental Webmaster Tools Labs feature that shows you latency information about your site. (To see Site Performance data, you must add and verify your site in Webmaster Tools.)

It shows you the average page load time for pages in your site, the trend over the last few months, and some suggestions on how to make the pages load faster. Page load time is the total time from the moment the user clicks on a link to your page until the time the entire page is loaded and displayed in a browser. It is collected directly from users who have installed the Google Toolbar and have enabled the optional PageRank feature.

All data is processed in aggregate without using or displaying any personally identifiable information. URLs displayed in the Example pages are collected from Google Toolbar. For privacy reasons, query parameters are stripped out. The URLs listed under Page Speed suggestions are based on pages crawled by Google. Their URLs are not truncated. The site-level "average" load time is traffic-weighted (i.e., more popular pages have a bigger say).