Steve Souders, Head Performance Engineering, Google

 Patrick Meenan, Google / WebPageTest

Steve and Patrick picked apart the performance of several UK Soccer Club websites with WebPageTest and Google Dev Tools.  Some things they covered;

• WebPageTest is open source, you can run your own instances, customize it.
• There’s an API, you can automate it when running your own instances.  Some people use this API for web test automation (selenium substitute).
• WebPageTest.org supports recording a video.  Do this.  It’s in the Advanced Settings, Video Tab.  It’s very compelling way of showing performance improvements or comparisons with competitor sites.
• You can do side-by-side comparisons in a filmstrip or video, via the Test History tab.
• If you have WebPageTest run the test from chrome, you can do a DevTools timeline capture.  
• DOMContentLoaded handling is purple vertical band in the WebPageTest waterfall chart.  It should be narrow, because the UI in not responsive during that event handling.
• The SPOF tab allows you to see what happens if one of your providers goes down (i.e. Twitter, Facebook, Bazaarvoice).
• Using window.onload as the measure for loading time is a little arbitrary, put that’s what is generally used as a criteria (used in PageRank).  Also, busy indicators stop at window.onload