Why isn't spell checking working on my new Firefox install?
It turns out there can be a variety of reasons and from my searches, the possible answers are not all in one place. This article is an attempt to put all the things to check in one place.
WARNING: I checked this on Fedora (GNU/Linux) and menu options may vary based upon your host operating system. Hopefully they are close enough to keep you on track.
The first thing to check is whether spell check is enabled at all. Select "Edit > Preferences" from the menu. Navigate to the "Advanced" tab and select the "General" subtab. Make sure the "Check my spelling as I type" option is enabled as shown in this figure:
If this option is selected, then we will have to check two more things which might not be correct. In order to do these you will have to navigate to a website which has a text entry form. Composing mail on a web mail client like Google or Yahoo mail will work. When you are there, right click in the text entry area and verify that "Check Spelling" is checked.
If it is, there is still one more thing to check. Apparently some Firefox distributions were shipped without dictionaries. If you installed one of these as a clean install, rather than as an upgrade, then you didn't get a dictionary. I don't know why and it doesn't really matter. If you have installed one of these versions, then you need to install a dictionary. Again, you need to right click but this time, select "Languages > Add Dictionaries". This will guide you through installing the dictionary you need.
As I was investigating this to help the person who asked, I learned I was using the "English / Zimbabwe" dictionary which I found surprising. It definitely explains why I use UK spellings frequently. It is necessary to make that language variant. Colour me surprised. Or color me surprised not that I am using "English / United States".
If there are any other things which might explain spell check not working in Firefox, please leave a comment.