With the rise of the mobile web, speed has become crucial to success. Users won't wait around for slow-loading pages and search engines are now punishing sluggish sites. There's a wealth of ideas out there for cranking up performance, but how do you know where to start? What if you work for days to ship an optimization that doesn't really pay off? In this talk, you'll learn how to experiment and fail fast. You'll find out how to quickly and rigorously assess your optimization ideas with open source tools, and how to share your results so that others can replicate your findings.