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/
Linux
~/.mozilla/firefox/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.

52 Comments
Neat trick. Maybe knowing this can help make a plug-in?
Thanks for this one. I accidentally added a word to the dictionary that didn’t belong. I really need to watch my click happy finger.
Thanks!
Hi,
I’m running OS 10.4.9 and only have a Mozilla folder inside the library folder which contains the file pkcs11.shlb and nothing else… any ideas?
Thanks a lot,
Amir, you should be looking for a Firefox folder, not a Mozilla folder.
Thanks for the quick reply.
Trust me, I did. There’s no Firefox folder inside the Application Support folder. I’m more than happy to provide a screenshot
You’re looking in your user folder and not the system Application Support, correct?
ooops
that did it. Thanks a lot!
THANK YOU!!! Man, I click the wrong damn line all the time and am constantly frustrated by the inability to remove those new wrong words from my dictionary!
Glad I could help Crystal.
Thank you! That was very helpful
Your instructions worked for Windows 2003 as well.
Thanks for the help.
Thanks a bunch, I was doing a search for a couple of days to try and find a solution for this, I went to correct word which I’d misspelled, I type in rush so at times tend to invert letters like “soemthing” and dang it, I added it
Very helpful, thanks.
THANKYOU!
I’ve been *way* too click happy and have quite an almost useless dictionary. This will help a *lot*. ^_^
What we need now is a plugin to move that evil add button somewhere else, or maybe the Mozilla folks can read this and learn what a pain in the posterior it is now.
Thanks a million! Awesome! Brilliant! Superb!
I’d added my first wrong word just the other day and had searched through the options within Firefox to try to undo it. Now 5 mins on internet looking how to fix it, or a new easier-to-use dictionary and I find the solution. Great Stuff!
I agree with “Aunty Nomus” we do need a plugin to move that evil add button somewhere else.
Thanks for the tutorial. FYI: You might need to close & reopen Firefox before you see the custom word in your persdict.dat.
I accidentally added an incorrectly spelled word to my dictionary, immediately googled the fix, & got this page. When I opened my persdict.dat, I didn’t see my word. After I restarted my Firefox, it came up. Hope that helps someone.
Thank you for this awesome writeup. I just encountered the same issue.
Thanks!!! This whole pointy-clicky thing is overrated
I’m in the folder but do not see the persdict.dat . I’ve checked my desktop XP and notebook Vista and the file is not there. Any ideas?
Firefox needs to be closed for persdict.dat to be visible. Also, if you didn’t add any custom spellings, the file will not exist.
thank you!! very useful
Many thanks for this, I was pulling teeth trying to find out how to edit the Firefox dictionary as I had a couple of misspelled words in there.
Thanks again
The feedback needs to be given to developers about this. The Add to dictionary button should have a confirmation dialog box.
Thanks for this, but I’m stuck…I can’t find my Firefox profile. Part of the problem is obviously that I don’t have an Application Data folder! (I’m using XP.) All I’ve got in there is Cookies, Desktop, Favorites, My Docs, Start Menu, UserData, and WINDOWS. I’ve tried to do a search but keep coming up with nothing.
Sorry, never mind. I didn’t realise the App Dat folder was sometimes hidden.
When coming to Application Data, it might be hidden. Do:
Tools -> Folder Options -> Show hidden files and folders -> ok. You may change it back later. Then you’ll see the folder Application Data if it was hidden.
When looking for ‘persdict’, note it doesn’t necessarily needs to show the .dat at the end. If t doesn’t, it’s the same file.
Thanks for that!
Okay, I’m the dunce here. I am running Windows XP Pro, and I do not seem to have an Application Data folder. I have used explore, I have used search. I have three users: one is [Administrator], one is [All Users], and [User].
So I get as far as Documents and Settings/[User] … and in none of those users do I find a folder called Application Data.
I, too, have a click-happy finger, and I have several common words in my dictionary that are now misspelled, and I would LOVE to remove them.
My apologies for being dense here.
Great!
New question: is there a way to edit the standard dictionary? I find all sorts of misspellings that seem to show up as obscure but correct English words. Every now and again I am dumbfounded by the mistakes I make that are not discovered, and they are not my own additons.
Thanks much!!
You’re not being dense at all. The Application Data folder is hidden by default so people don’t mess with it by accident. Here’s a good guide for making it visible.
That’s an excellent question. Unfortunately, I don’t have a solid answer for you.
After some quick poking around, I found a en-US.dic file and a en-US.aff file. Both files open in a standard text editor, but are not just a basic list of words. They contain some extra data. You may be alright just deleting the line containing the word you want to remove, but I can’t be certain. Make a backup of both files before proceeding.
On Mac I found the file at:
I have no clue where those files are located on Windows, but I would assume the Program Files/Mozilla Firefox folder.
thanks…. nice and very clear…
Weird; I just added “occurance” to my dictionary and found this article, looked in the file, and only the words I had purposefully added had made it there o.o
Oh well, I may not have needed it this time around, but it’s good to know for the future!
i don’t have a persdict.dat file in that folder, or anywhere else on my computer. but i do have a dictionary and i did add a word by mistake. what do i do?
Are you looking the correct user folder? If so, the file will not exist if no custom words have been added to the dictionary. Are you positive the accidental word actually made it into the dictionary?
Thanks, appreciated the useful bit of info
thank you!!! I had 5 in there and really wanted to fix it… much appreciated!
Thanks! This should be an add-on.
Thanks - great tip….
Thanks a ton for this. Insane how this is the only way to do it eh?? Create a short cut of the DAT file to your desktop for easy access as well.
thanks a ton. i somehow managed to add 2 words today that didnt belong and couldnt figure this out for the life of me.
For Windows users I suggest typing the following, it will get around not seeing hidden files/folders, is not specific to the user and is shorter. Environmental variables are your friend.
%appdata%\Mozilla\Firefox\Profiles\
then browse down through the *.default folder, close Firefox and edit away.
Thank you for this! I love the internet.
Thanks so much. I accidentally added a misspelled word to the dictionary and was able to remove thanks to this post. Very much appreciated! =]
Thanks a ton for this. Got my dictionary all fixed up.
Thanks much for this! I too had accidentally added misspelled words to the dictionary and I was able to remove them. We truly need a Firefox plug-in for this!
Thank you - this has helped me several times already.
THANKS!!! I accidentally added two words in two days!!!
Brilliant stuff. Thanks for this tip.
I find it wherry annoying that i have to use Google to find the right spelled word when the firefox speller suggest totally inappropriate alternative words.
Are there any way to add to the suggested word list?
Thanks a lot, mate. Had a bunch of blunders I’ve been wanting to ditch for awhile. The update to Firefox 3.o yesterday seemed like a good time to figure out how.
This page was the top result on a G-Search of edit firefox spelling dictionary, so I’m sure you’re happy about that.
Cheers from Lancaster PA!
This tip was a huge help. In addition, you can add words in the text editor that you know should be added like long last names and scientific terms.
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