Around this time last year, Mozilla and Epic Games showed off the Unreal 3 game engine running in the browser, using a combination of the WebGL 3D graphics API and asm.js, the high performance subset of JavaScript. Commercial games built using this technology were launched late in the year.

With this apparently successful foray into using the browser as a rich gaming platform, Mozilla and Epic today demonstrated a preview of Epic's next engine, Unreal Engine 4, again boasting near-native speeds. The Web version of UE4 uses Emscripten to compile regular C and C++ code into asm.js.

Over the past year, Mozilla has improved asm.js' performance to go from around 40 percent of native performance, to something like 67 percent of native. Our own testing largely supported the organization's claims, though we noted certain limitations at the time, such as JavaScript's lack of multithreading.

Mozilla promotes NomNom Games' Monster Madness, the first commercial Unreal 3/asm.js Web game, as a demonstration of how the technology can be used successfully. Jeremy Stieglitz, CTO at NomNom Games, said that it took just a day to port the game to the Web and that the ease of access made it an instant hit among its users, with more than a quarter of players using the Web version.