How Do I Add a Custom Language in Firefox?

Question

Firefox has a list of built-in languages that are used to set the HTTP_ACCEPT_LANGUAGE header. How do I add a custom one that's not on the list?

Answer 1

Is this what you're looking for?

Tools -> Options -> Content ->  Languages -> Select a language to add

It's from a similar post.

EDIT:

As far as I can tell, this GUI option just changes the preference "intl.accept_languages" in about:config. You could edit this yourself to change it to a custom value. I'm not sure if you can put language files somewhere to get a custom language to work or not.

Answer 2

You can use about:config to edit the list of language codes:

Enter about:config into address field, find the setting *intl.accept_languages*. Its value is the list of language codes to send as "Accept-Language". The list is comma-separated in descending priority. You can enter any code you like; the codes will even be displayed in the standard pref dialog (see mouche's answer), where you can delete them later (just not add them).

As an aside: Why do you need this? I have never encountered a website that supports more than the (extensive) set of standard tags as defined in ISO-639. Which special tags do you want to use, and why?

Answer 3

Firefox has a section on their website where you can download and add custom languages to your Firefox:

https://addons.mozilla.org/en-US/firefox/browse/type:3