Firefox apparently blacklist certain combinations of GPUs and/or drivers from running WebGL content, which throws out the following erros to the browser's console: Code (CSharp): Error: WebGL: Error during ANGLE OpenGL init. UnityConfig.js:30:18 Error: WebGL: Refused to create native OpenGL context because of blacklisting. UnityConfig.js:30:18 Error: WebGL: WebGL creation failed. UnityConfig.js:30:18 And then pops up a Message Box that says which will understandably lead to some very confused players and needless support tickets, so better error handling here would be nice. The video card used in this case was a 9800M.