This document discusses client-side performance testing. It describes measuring client-side performance through synthetic monitoring tools like WebPageTest.org, SiteSpeed.io and ShowSlow which test page load speeds, and real user monitoring through Akamai RUM, Monitis RUM and Google Analytics. WebPageTest.org is demonstrated in more detail, showing how to use it to test pages and understand key metrics like time to first byte, time to start render and full page loaded time. Private instances and automation of WebPageTest is also covered. YSlow and Google PageSpeed are also mentioned as alternatives for measuring client performance.