How do I remove the English (United States) dictionary from Firefox? It's not an add-on so I'm guessing it's built into Firefox by default. Maybe that makes it unremovable?

I noticed whilst typing a Hotmail email in Firefox that the default language seems to be English/United States. As I am from the UK I thought I would add in the English/United Kingdom dictionary, which I have. This is now the default language and I don't need the US dictionary.

Firefox 3.6.2 on Windows 7 Home Premium 32 bit.

4 Answers 4


The dictionaries are stored in the dictionaries folder in the Firefox program folder (C:\Program Files\Mozilla Firefox\dictionaries) and you can remove the files from that folder.

The Mozilla Add-ons Dictionaries page is displayed. To add a dictionary to your Firefox installation, click the "Install Dictionary" link next to the dictionary you want to add. The Software Installation window appears. When it is displayed, click Install Now, which should open the Add-ons window, where you'll see the dictionary being installed.

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To enable the dictionary, click the Restart Firefox button, in the Add-ons window. You can even see for more here.

  • NB: this will be under Program Files x86 if you are running a 64 bit windows
    – Anigel
    Commented Sep 11, 2014 at 4:28

To remove the en-US dictionaries so that they are no longer accidentally triggered, and to ensure that your chosen dictionary is used at all times, do the following:

  1. Shut down Firefox.
  2. Go to your install directory (“Mozilla Firefox”, usually under “C:\Program Files” in XP).
  3. Look for the “dictionaries” folder.
  4. In that folder, you will find the files:
    • en-US.aff
    • en-US.dic
  5. Delete or remove these two files out of the folder.
  6. Restart Firefox.
  • 4
    Excellent answer, thank you. The problem is that unless you do this anything that non-US users type in a text box will randomly switch back to "English (United States)". It's ridiculous that you have to manually delete files to get basic functionality like language selection to work 24/7. The other problem is that I believe that these files regenerate every time there is a Firefox update (every 3 hours isn't it? {sardonic scowl}) since I know that I've deleted them before based on this answer so next time I find them I'm going to write a scheduled task to purge the accursed things.
    – Alan K
    Commented Apr 28, 2013 at 0:54
  • Thanks will also make a scheduled task, I found my firefox keeps randomly switching back to the en-us dictionary.
    – Chris C
    Commented Sep 6, 2023 at 23:24

Just to note for the record, the above file location isn't always where the dictionaries are found.

I found them in C:\Users\<My username>\AppData\Local\Mozilla Firefox\dictionaries presumably because it's a corporate computer.


FYI, for OS X users, the default US dictionaries are found in /Applications/Firefox.app/Contents/MacOS/dictionaries.

  • In firefox 34.0 and OS X 10.10.1 it seems that the defaults ones are here /Applications/Firefox.app/Contents/Resources/dictionaries
    – LyK
    Commented Dec 11, 2014 at 18:10

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