The performance of your web app is obviously important. But how do you know your web app is performing well for all of your users? Out of the box tools provide us metrics, but most only provide an overall view. This case study of building the XFINITY X1 single-page web app will demonstrate what frontend performance data you should be gathering, how to gather it, and how to make sense of all that data. Existing tools provide insight into the performance of our web applications, but there is not a single tool that gives you the full picture. You can fill these gaps by gathering the performance data of your actual users. In this talk, we'll walk through the parts of the W3C Navigation Timing, High Resolution Time & User Timing recommendations that you can easily take advantage of right now to collect important metrics (with the help of Open Source software). We'll determine the "types" of users you need to focus on to understand your web app, as well as what other factors could impact those individual users' experiences. And we'll make sure "Average Response Time" is never the primary focus of your metrics dashboard.