Since yesterday my Firefox thinks that everyone in Belgium speaks Flemish. This is a typically American problem: Americans NEVER seem to know where languages are spoken (I think they just guess), but for some reason believe that language localization software is cool.

It is NOT; it is a curse. So suddenly I no longer have my user interface in English (which was fine), but now in Flemish, which looks and reads like a tongue disease and is not even the second language of the area I live in (the first language here is German and second is French). How can I change back to English?


You should install an English language pack. A language pack is a Firefox add-on.

You can download it from here. Then you must install it like any other add-on ("install add-on from file" in the add-on interface).

Then you should change the language preference. You can do this by typing about:config in the Location bar (address bar) and then searching for


And change that to:


(the same name as the downloaded .xpi) Then you must restart the browser.

More details at: http://kb.mozillazine.org/Language_packs

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    I tried this solution in Firefox Quantum 60 (64 bit) on Windows 10, but didn't work. I could install the language page, but the "general.useragent.locale" key didn't show up in the about:config list. However, I could add the key manually with value "en-US", and that changed the UI language. – b_jonas May 15 '18 at 8:31

Install en-US https://addons.mozilla.org/en-US/firefox/addon/english-us-language-pack/ and have key intl.locale.requested set to en-US in about:config.


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