Firefox automatically checks the spelling of words that you enter in text boxes containing more than one line. As soon as you finish typing a word, it is checked against the words in the installed dictionary. If the word is not found in the dictionary, it will be underlined in red, as in the following example:

Note: Automatic spell-checking is only turned on for text boxes containing more than one line, where you can enter as much text as you want.

Disabling automatic spell-checking

By default, Firefox is configured to automatically check spelling. You can turn it off in the OptionsPreferences window:

1. In the Menu bar at the top of the screen, click Firefox and then select Preferences or Settings, depending on your macOS version.Click the menu button and select Settings.
2. Select the Advanced panel.
3. Click the General tab.
   
   
   
   
4. Select Check my spelling as I type.
5. Click OKClose the preferences window.

Correcting misspelled words

When spell-checking is enabled, you can easily correct misspelled words. To correct the misspelled word, right-clickhold down the Ctrl key while you click on it and select one of the suggested words at the top of the menu.

If none of the suggested words is appropriate, you must manually edit it. If you are sure the word is spelled correctly, you can add it to the dictionary. To add a word to the dictionary, right-clickhold down the Ctrl key while you click on it, and select Add to Dictionary.

Adding dictionaries

You can install other dictionaries as necessary.

1. Right-clickHold down the Ctrl key while you click in any text box containing more than one line.
2. Select Languages.
3. Select Add dictionaries....
   
   
   
4. 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.
   
   
   
   
5. To enable the dictionary, click the Restart Firefox button, in the Add-ons window.

Switching dictionaries

After the dictionary is installed, you can switch to it, as needed. To switch to a different installed dictionary, right-clickhold down the Ctrl key while you click in a multi-line field, select Languages, then select the dictionary you want to use.

Removing a word you have accidentally added

1. Open your profile folder:

   • Click the menu button , click Help and select More Troubleshooting Information.From the Help menu, select More Troubleshooting Information. The Troubleshooting Information tab will open.
   • Under the Application Basics section next to Profile FolderDirectory, click Open FolderShow in FinderOpen Directory. A window will open that contains your profile folder.Your profile folder will open.
   Note: If you are unable to open or use Firefox, follow the instructions in Finding your profile without opening Firefox.

2. Click the Firefox menu and select Exit.Click the Firefox menu at the top of the screen and select Quit Firefox.Click the Firefox menu and select Quit.
3. Open the file persdict.dat in a text editor. (Such as Wordpad)
4. In the text editor each word you've added is on a separate line. Remove the line, containing the word you wish to remove.
5. Click the File menu, and select Save, to save your work.