Speaking to some of the Google developers and the head of mobile web performance - not even Google use their own tool as a measure / benchmark for performance. PageSpeed Insights is both broken and convoluted at best.<p>- No support for HTTP/2
-- This means that if you follow all the "right" approaches for performance with HTTP/2, you'll be slapped with a terrible PageSpeed score due to it not taking into account the effect of multi plexing connections.
- Has constant bugs around determining the flow of assets on the page and thinks that assets at the bottom become render blocking when they do not<p>Google tend to use a combination of their own tooling + WebPageTest.org (which is also theirs) to test performance issues.<p>This tool is mainly geared at the non-developer type, but it's unfortunately misleading and just wrong. It doesn't measure speed, it measures performance methodologies and whether they have been implemented or not (and old ones at that).<p>The more important metrics are time to paint, time to domcontentready. Using WebPageTest will get you what you want. I find it pretty offensive and misleading that Google is using such a tool and promoting it to users, because frankly it misses the entire point of performance.<p>Things like this:
"Eliminate render-blocking JavaScript and CSS in above-the-fold content" when you're running an H/2 site with an appcache and pushing assets is just downright wrong.<p>It's sad that there's a general miscommunication within the company about performance. Ilya Gregorik and co say one thing, and the rest say another.