http://www.mozilla.org/support/firefox/faq.html How do I spell Firefox? How do I abbreviate it? Firefox is spelled F-i-r-e-f-o-x - only the first letter capitalized (i.e. not FireFox, not Foxfire, FoxFire or whatever else a number of folk seem to think it to be called.) The preferred abbreviation is “Fx” or “fx”.