Page Speed is an open-source project started at Google to help developers optimize their web pages by applying web performance best practices. Page Speed started as an open-source browser extension, and is now deployed in third-party products such as Webpagetest.org, Show Slow and Google Webmaster Tools.
It is available as extensions for Chrome/Firefox:
Here is the download link:
Apart from this if you want to embed page speed in other applications then here are the instructions:
But the best thing is.....Page speed in now available online. This means you can analyze the web performance without downloading anything.
Optimize for mobile: Due to the limited CPU capabilities of mobile devices, the high round-trip times of mobile networks, and the rapid growth of mobile usage, it is even more critical to understand and optimize for mobile performance than for the desktop. Page Speed Online now allows you to easily analyze and optimize your site for mobile performance.