Learn basic and advanced uses of WebPagetest, the performance measurement tool for optimizing websites. This practical guide shows users new to this tool how run tests and interpret results, and helps experienced users gain a better and more thorough understanding of hidden features in WebPagetest that make testing easier. Written by WebPagetest power users and performance experts, this book will help web developers and frontend engineers solve the problem of slow sites. Topics include: Basic test setup—shows beginners how to get meaningful results Advanced test setup—provides another level of technical depth by explaining features not thoroughly documented at webpagetest.org Analysis of results—helps you understand of how to interpret test results Private instance setup—teaches power users the intricacies of the webpagetest private instance and how it works API and external tools—provides a detailed reference for the API and demonstrates tools already using the API to extend WebPagetest