HTML5 Rocks - New Tricks in XMLHttpRequest2 Introduction One of the unsung heros in the HTML5 universe is XMLHttpRequest . Strictly speaking XHR2 isn't HTML5. However, it's part of the incremental improvements browser vendors are making to the core platform. I'm including XHR2 in our new bag of goodies because it plays such an integral part in today's complex web apps. Turns out our old friend got a huge makeover but many folks are unaware of its new features.