Epic Games has launched a public version of Epic Citadel, their engine demo, as a web-based application that requires no plug-ins to run, as it is built on standards-based technologies like HTML5, WebGL, and JavaScript. As such it should run in any browser, though for the moment it seems to favor Firefox Nightly version 23 or above, because with all that talk of standards and lack of plug-ins, it also makes use of "optimizations for asm.js, a highly-optimizable subset of JavaScript pioneered by Mozilla, whose performance can rival native code." The Unreal Engine website has further details on this.