Google has released a new tool called Page Speed Online to help you analyze and improve your site’s performance. While not as detailed as webpagetest.org it does provide a good idea of where you are and how you can improve. In addition, it is far quicker than the exhaustive tests ran by webpagetest.org. I’m going to experiment with it over the next few weeks and see if it can help me lower the load times of any of my sites.
As you can see the output from the two is quite different. While webpagetest.org is much more detailed, it also tends to be rather inconsistent (the D for combining CSS has been everything from an A to an F on different tests without changing anything). In addition, webpagetest.org doesn’t take into affect factors such as Google Adsense scripts and others and will in fact count them against you. I am not certain yet how Page Speed Online will handle this type of content.