In Chrome, PageSpeed Insights extension runs in theChrome Developer Tools.
Supports Mac OS X (x86), Linux (x86 and x86-64), and Windows (XP and up)
Run PageSpeed Insights against your web pages
Follow the instructions to use PageSpeed Insights in Chrome or Firefox. When you visit a web page, open PageSpeed Insights and click "Analyze Performance" to get a performance report for that page. PageSpeed will present you with a set of rules and recommendations. Before you start changing the scripts and resources on your pages, press on the rule to understand what it is pointing out and its background.
Get familiar with the tool. There are a number of features that are easily accessible from the menus of the extension. In particular, for the Firefox extension, in the top tab called "PageSpeed", a caret next to the text gives you the ability to set preferences for how PageSpeed runs and where it saves optimized resources.