PageSpeed Insights analyzes the content of a web page, then generates suggestions to make that page faster. Reducing page load times can reduce bounce rates and increase conversion rates.
For Chrome users: Pagespeed Insights is a built in feature. You can access it by opening the developer tools via Tools > Developer Tools.
Ranked in these QuestionsQuestion Ranking
Pro Provides mobile pagespeed score as well
Considering the fact that a large fraction of people nowadays visit websites from mobile devices, it is very important that your site performs well on mobile browsers too. To help you with increasing your site's performance in the mobile arena, Google Page-speed has you covered, it'll test your site with respect to mobile platforms and provide you a detailed report of your current score and what you can do to improve it.
Pro Provides a very detailed report of its findings
Once you test your website using Google pagespeed online, it not only gives you a score of how fast your website is, but also what you can do to improve it. These optimization tips can range from minifying assets and optimizing images to leveraging browser caching. Following these you could improve, not only your pagespeed score but also your rank in Google search results
Con No option for location of test
Even though Google's Pagespeed Insights does quite an amazing job as a speed profiler, currently it doesn't provide you with the option of analyzing your website from a specific location.
Con Limited actionable data
Provides unhelpful instructions like "eliminate blocking JS", well duh, but what JS is blocking? Without a waterfall/HAR like the other's GPS is seriously lacking in usefulness.