Super User is a question and answer site for computer enthusiasts and power users. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

How do I delete a false entry from the Firefox dictionary?

I have added five false entries to the dictionary by mistake.

share|improve this question
up vote 8 down vote accepted

Edit Firefox’s Spelling Dictionary

If you have used Firefox’s built in dictionary, you will know there is a limitation to it. Firefox allows you to easily add words to dictionary, but lacks a user interface for removing words. This can be a problem since the “Add to dictionary” button is directly under the corrected words, providing easy access for adding misspelled words to the dictionary.

Since I frequently add misspelled words, I had to learn the method for removing these words. To remove misspelled words, first close down Firefox then navigate to your profile folder. The folder’s location varies depending on your operating system:

Windows XP

C:\Documents and Settings[User Name]\Application Data\Mozilla\Firefox\Profiles\xxxxxxxx.default\

Windows Vista

C:\users[User Name]\AppData\Roaming\Mozilla\Firefox\Profiles\xxxxxxxx.default\

Mac OS X

~/Library/Application Support/Firefox/Profiles/xxxxxxxx.default/



Once in your profile folder, look for a file named persdict.dat, and open it with your favorite text editor. Inside you’ll find all of your custom defined words, each on their own line. Just delete the words which don’t belong and save. Firefox will no longer incorrectly identify those misspelled words as correct.


share|improve this answer
Excellen answer, thanks. – OscarRyz Oct 23 '09 at 20:06
From time to time I need to re-read this answer :P Too bad I can't upvote it each time. – OscarRyz Dec 9 '09 at 18:11

From the always useful Lifehacker:

  1. Open your application data folder. On XP or Vista, go to your Start menu and hit Run (or just press Windows-R) and paste in %APPDATA%\Mozilla\Firefox\Profiles; on your Mac, navigate to ~/Library/Application Support/Firefox/Profiles.
  2. Find your profile folder, which by default should look something like xxxxxxxx.default.
  3. Inside your profile folder, find the file called persdict.dat and open it up in your text editor of choice.
  4. Now just find the misspelling, delete it, and you're done.
share|improve this answer
This still works in Firefox version 44.0.2 (2016-02-12) - though the profile folder does not necessarily end in ".default"; a sample name is "yynxpuma.default-1439568940109". – Peter Mortensen Feb 13 at 18:28

See "Firefox Dictionary & Spell Checker Hacks: Edit Misspelled Words, Merge with Word Dictionary". Basically, you need to manually edit the file named persdict.dat.

share|improve this answer

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .