Webpagetest vs Google Pagespeed Insights Online

You can dig deep into your results down to the root to find out what are the issues that are leading to your website being slow. There are a lot of options which you can select to narrow down your results namely timelines, content breakdowns, processing breakdowns and incredibly detailed performance reviews.

If you'd like to go a step ahead of just speed profiling your site and see how not only how it performs but also how it appears on different browsers, Webpagetest would be the best option for you. Due to its vast range of browsers available (From IE7 to Chrome on Android or even Safari on iOS)

If your website serves visitors only from your own city or country. It'll be a good idea to speed test it using one of Webpagetest's servers in or near to your area.

Provides an excellent user perception metric, Speed Index, of how much content above the scroll is completed quickly.

Can be set to provide a film strip of the page loading

Often sites in development are protected behind basic auth

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.

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