Do you have a dictionary installed and selected?

You can see which dictionary is selected if you right-click in a text area and open the Languages sub menu. At least one dictionary should be installed and have a check mark to indicate that it is selected.

• open the "Add Dictionaries" link to install a dictionary if you do not have one.

The spelling checker is enabled if [X] "Check Spelling" in the right-click context menu has a checkmark.

You can enable or disable spell checking globally:

• Options/Preferences -> General: Language and Appearance: "Check your spelling as you type"

You can look here for dictionaries:

• https://addons.mozilla.org/firefox/language-tools/

Note that you need a dictionary and not a language pack that provides string translations for the user interface.

You can check the layout.spellcheckDefault pref on the about:config page.

• http://kb.mozillazine.org/layout.spellcheckDefault

I tried all that, it still isn't working.

opalizea said

The wavy red line appears under misspelled words... but nothing happens when I click on it. ...

How about a right-click on the misspelled word?

Then correct spelling suggestion should appear.

Nope.

What do you see if you right-click ?

Is there a dictionary selected (which one) ?

Start Firefox in Safe Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration is causing the problem.

• switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Themes
• do NOT click the "Refresh Firefox" button on the Safe Mode start window

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

I see nothing when I right-click. I might as well be not clicking at all.

okay refreshing firefox seems to have worked