As another commenter here pointed out, it's preferred, not correct. This is the old prescriptivist vs descriptivist debate, as seen among linguists. (Disclaimer: I am not a linguist. I just read Language Log.) If you're fretting about the correct this and the proper that (prepositions at the end of sentences, "whom" instead of "who", and so on), you're a prescriptivist, and you may (note, I said may) be making up rules where no rules are needed. I prefer descriptivism (as in: "nauseous" now means the same thing as "nauseated", which is different from its old meaning of "nausea-making", because that's how it's used).

(Edit: "different to" sounded wrong. I could never remember which way that goes.)

The whole planet says "FF". This makes it de facto the correct/preferred/official abbr

I think they need to change their FAQ. I've never seen it abbreviated as Fx -- only as FF.

The FAQ says preferred not correct though. But it feels unnatural. Having media background FX for me at least means "effects" (as in special effects). Firefox may be written as a single word but there are two words in there and the natural way would be FF IMO. I have seen someone use Fx once and it confused the heck out of me... sorry Mozilla, I will use FF..

Searching "FX" on Google brings nothing related to Firefox, not a single link, but "FF" brings Firefox download page. Sorry but I'm going to stick with FF.

…and “GIF” is supposed to be pronounced “JIFF” …and “npm” doesn’t really stand for “Node Package Manager”

sigh

I'm sure they'll convince everyone in the world before the end of time.

I don't think there's many situations where you'd have to abbreviate Firefox anyway, it's not a large word to begin with. Internet Explorer as IE I can understand, it's large and compounding it is useful - but we don't abbreviate Opera or Chrome?

In related news they would prefer we use FrskQet instead of FAQ

I wonder if they were inspired by Steve Wilhite (creator of the "jif").

FF is faster to type. I doubt most people who abbreviated it will change to Fx.

I'm looking through their bug reports and developer message boards all of the time... and I've never seen anyone abbreviate it as anything other than "FF".

Ugh, shut up, nobody cares. Hey, maybe start taking care of your God-awful rendering engine and CPU cycles instead of wasting time on stuff like this?

I use ffx, because unambiguity

Good luck with that, Mozilla.

Well, that page is wrong.

What about Fifx :)

What was the point of showing this here?