Extensions, themes, and plugins are all types of add-ons for Firefox. This article describes how to disable and remove add-ons in Firefox.
Disabling an extension or theme will turn it off without removing it:
Click the menu button
and choose Add-ons. The Add-ons Manager tab will open.
To re-enable the add-on, find it in the list of Add-ons and click Enable, then restart Firefox if required.
Beginning with Firefox version 52, support has ended for all NPAPI plugins except for Adobe Flash. See this compatibility document and this article for details.
To re-enable the plugin, find it in the list of Plugins and select Always Activate in its drop-down menu.
Most plugins come with their own uninstallation utilities. For help uninstalling some popular plugins, go to this list of articles and select the article for the plugin you want to uninstall.
For related discussion about this article, see:
I replaced the way to open the AOM, fixed a broken link, make screenshots only for fx35, added a summary and keywords. It needs review.
Michael Verdi made a small edit to your revision and approved it:
Revision id: 16726
Created: Aug 26, 2011 2:45:49 PM
Ready for localization: No
Reviewed: Aug 26, 2011 2:46:17 PM
Reviewed by: Verdi
Is approved? Yes
Is current revision? Yes
The existing article is as follows:
How to disable extensions and themes
"At the top of the Firefox window, click on the Firefox button, and then click Add-ons. The Add-ons Manager tab will open."
There isn't a Firefox button. The current procedure is:
1. Click on Help In the Menus toolbar (at the top)
2. In the drop-down menu click on Restart Firefox with Add-ons Disabled...
That instruction is listed for Windows 7/Vista as most Firefox browsers installed on that OS has the Firefox button. If you are using Windows XP, Mac or Linux, you will see the instructions to use Tools to get the add-ons manager.