Extensions that do not have a "Remove" button are installed by other software and are not under control of the Firefox extension manager. Such globally installed extensions are usually found via a registry scan or are installed in a location that Firefox scans for installed extensions.

• https://developer.mozilla.org/Installing_extensions
• https://developer.mozilla.org/Adding_Extensions_using_the_Windows_Registry

Extensions installed this way need to be removed via the settings (options/preferences) of the program that has added this extension or this program has to be uninstalled via "Control Panel > Programs". In Firefox you an only disable such an extension.

It is possible that there is a problem with files in the profile folder that store the extensions registry.

Delete the extensions.* files (e.g. extensions.json, extensions.ini, extensions.sqlite) and compatibility.ini in the Firefox profile folder to reset the extensions registry.

• https://support.mozilla.org/kb/Profiles

New files will be created when required.

See "Corrupt extension files":

• http://kb.mozillazine.org/Unable_to_install_themes_or_extensions
• https://support.mozilla.org/kb/Unable+to+install+add-ons

If you see disabled or not compatible extensions in "Firefox menu button/Tools > Add-ons > Extensions" then click the Tools button at the left end of the Search bar to check if there is a compatibility update available.

If this didn't help then delete addons.json and possibly prefs.js in case there is a problem with preferences.

You can use this button to go to the current Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)
• http://kb.mozillazine.org/Profile_folder_-_Firefox

It's not that the extensions don't have a 'remove' button, it's that the Extensions tab isn't listing the extensions. In previous versions of Firefox all the add-ons that I would get from 'get add-ons', when installed, would be listed in the Extensions tab. That's where I would see an enable/disable button and an uninstall button. I've got add-ons like AVAST DuckDuckGo, Adblock Plus, No Squint, LastPass and several others.

So now, when I open the menu on the top right side of the toolbar, I click on the Add-ons option and a menu of tabs comes up: Get Add-ons (which takes me to the add-ons page), Extensions (which says 'you don't have add-ons of this type installed'), Appearance (which has 4 personas I've used), Plugins (which has 7 plugins listed including Acrobat and Google Talk), and Services (which tells me the same thing that I read on Extensions, 'you don't have add-ons of this type installed').

The Extensions tab should have my AVAST, DuckDuckGo, AdBlock Plus and others which I got via 'Get Add-ons' listed with their uninstall button options. But as I've said in the above paragraph, there is only a message saying that I do not have these type of add-ons installed. Except that I do have them installed and they work. So if they are somewhere other than the Extensions tab on this latest version of Firefox, where are they?

Did you try the second part of my above reply to check for issues with the extension registry files?

Yes cor-el, it worked. I would never have figured that out on my own. Thank you.

One can easily remove add-ons, plugins or extension from their web browsers. As you have asked to get rid of add-on and other extension from your Mozilla Firefox, then you can follow the guides and tutorial mentioned here - Remove Add-ons using Add-On Manager of Browsers