How-To

How to Use the Firefox Spell Checker

By Adam Davidson

Published April 4, 2023

Want to avoid embarrassing typos when you’re filling in online forms? Learn how to use the Firefox spell checker.

We don’t tend to do a huge amount of typing in our web browsers. That is, of course, unless we’re using online word-processing apps or we’re busy sharing our important thoughts on social media.

Even so, when you’re filling in online forms, it can be useful to know that you’re not including a ton of spelling errors in your strongly worded message to customer services. Thankfully, Firefox comes with its own spell checker to point out any howlers before you hit submit.

If you want to know how to keep the typos out of your online forms and social media posts, learn how to use the Firefox spell checker below.

What is the Firefox Spell Checker?

Firefox has a built-in spell checker that compares what you type when using the browser to its dictionaries. If it spots any words that it believes are spelled incorrectly, it will underline them. You then have the option of correcting the underlined word to one of Firefox’s suggestions. You can choose from a range of available dictionaries, and even add your own words to the dictionary, too.

The spell checker is on by default, but it is only active in text boxes that contain more than a single line. Any typos you put in single-line text boxes won’t get picked up.

How to Correct a Word in Firefox Spell Checker

Correcting a word in Firefox can be achieved with just a couple of clicks, making it simple to fix any spelling errors that Firefox may find.

To correct a word in Firefox:

1. Find a word that has been underlined in red by the spell checker.
   
2. Right-click on the misspelled word.
3. Select one of the suggested words from the drop-down that appears.
   
4. The corrected word will now appear in your text field.
5. If the underlined word is spelled correctly, you can opt to add it to the dictionary. This will stop it from being underlined in the future.
6. To add a word to the dictionary, right-click on the misspelled word and select Add to Dictionary.
   
7. Any words you add to your personal dictionary will apply across all the dictionaries you may be using.

How to Add Dictionaries to Firefox Spell Checker

Firefox will use a default dictionary for your locale, but if you also write in other languages or dialects, then you can add additional dictionaries for the spell checker to use.

To add a dictionary to Firefox:

1. On a webpage in Firefox, right-click on any text box that is more than a single line.
2. Click Languages and then select Add Dictionaries.
   
3. A new page will open. Select the dictionary that you want to add from the list.
   
4. Click Add to Firefox.
   
5. To confirm that you want to install the dictionary, click Add.
   
6. The dictionary is now added to Firefox.

How to Switch Dictionaries in Firefox Spell Checker

If you add additional dictionaries, you’ll need to let Firefox know which dictionary it should be checking against. It’s easy to switch between dictionaries so that you’re using the most appropriate one for the text that you’re typing.

You can even select multiple dictionaries to check your text against multiple languages at once.

To switch dictionaries in Firefox:

1. In Firefox, right-click in any multi-line text box.
2. Click Languages and select the dictionary you want to switch to.
   
3. You can select multiple dictionaries at once. Any dictionary that has a checkmark next to it will be used in the spell checker.
   
4. To stop using a dictionary, click it again so that it is unchecked.

How to Remove Added Words from Firefox Spell Checker

You may add words to your dictionary, only to realize that you had in fact got the spelling wrong all along. In this case, you’ll want to remove the word from your dictionary so that the spell checker will highlight it as a misspelling in the future. This isn’t as easy as you might expect and involves directly editing the word list saved on your computer.

To remove added words from Firefox:

1. Click the Firefox menu icon.
   
2. Click Help.
   
3. Select More Troubleshooting Information.
   
4. Find the Profile Folder row and click Open Folder on Windows or Show in Finder on Mac.
   
   
5. Scroll down to the persdict.dat file.
   
6. Open the file with a text editor app. To do so on Windows, right-click and select Open With.
   
7. Click More Apps.
   
8. Select Notepad and click OK.
   
9. Before you make any changes, close Firefox.
10. In the text editor, find the word you want to remove from the dictionary.
    
11. Delete the word and press Ctrl+S (or Cmd+S) to save the file.

Make Firefox Your Own

Learning how to use the Firefox spell checker ensures that you never enter embarrassing typos in online forms ever again. It’s a useful tool that you can customize to meet your own particular needs.

There are other ways to customize Firefox, too. You can select the search engines that you use in Firefox. You can create and manage multiple profiles in Firefox. And if you want to get really down and dirty, you can access and change hidden advanced settings in Firefox.