The Mozilla Firefox Youtube channel recently uploaded a small clip showing the Unreal 4 Engine running in their browser. The new Engine will support both OpenGL and WebGL rendering. The first one should enable the engine to run on the three major operating systems, namely Windows, OSX and Linux. The latter means that in-browser support is also available, and running at almost the same performance as its OpenGL counterpart. The possibility of having an in-browser game that can compete with QuakeLive looks very promising. You can find the Youtube video in the full article.