From MozillaZine Knowledge Base
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Revision as of 11:25, 29 June 2012
This article explains how to uninstall extensions and themes you no longer want. If you are troubleshooting possible problematic extensions you should first try disabling the add-on.
Note: Be careful when installing or updating other applications, which may include a toolbar or other add-on by default. A list of applications that come bundled with unwanted add-ons can be found here and here
Uninstalling extensions and themes
The usual method for uninstalling extensions and themes is by using the Add-ons manager for your Mozilla application, as follows.
Uninstalling an extension might not completely remove all of the extension's data. For example, if you reinstall the extension, then you might find that it still uses its previous settings. There is no general way to remove all of an extension's data. See Resetting preferences for how to remove added preferences and restore the default preference values.
If you have trouble uninstalling an extension or theme from the Add-ons manager:
Corrupt extension files
It's possible that the files that store information about your installed extensions are corrupt, preventing you from updating or uninstalling an extension. To resolve this, close your Mozilla application and delete (or rename) all extensions.* files from the profile folder, which may include the following:
Note: The specific extensions.* files found will depend on your Mozilla application and version. Deleted or renamed files will be regenerated upon application restart, as needed. You may also have to delete the "compatibility.ini" file to rebuild some other files in the profile folder. 
If you are unable to uninstall an extension, even after restarting your Mozilla application in Safe Mode:
Exit your Mozilla application, go to your profile folder and open the "extensions" directory. Each directory there is an extension. Remove the directory that corresponds to the extension you want to uninstall. (To uninstall ALL extensions, remove the entire "extensions" directory)
If an add-on directory there does not have a meaningful name, look inside it for its "install.rdf" file. Open that file in a text editor (such as Notepad) to see which extension the directory contains. Alternatively, in the parent folder, "extensions.rdf" contains a list of extensions, their names and corresponding GUIDs.
Note: Starting in Gecko 2.0 (Firefox 4 / Thunderbird 3.3 / SeaMonkey 2.1), XPI files are no longer unpacked when extensions are installed. Instead, the XPI itself is placed in the extensions directory, and files are loaded directly out of the package. See Updating extensions for Firefox 4 for details. 
In a few cases, an extension may be installed globally into the Mozilla installation directory. Installing a global extension is something an administrator might do so that the add-on can be used by any user on the machine. It is also possible that another software installation may have included a global extension (for example, the Java JRE installer adds a global extension to Firefox, for the Java Console ). To manually uninstall a global extension, open the "extensions" directory in your Mozilla application's installation directory and remove the directory that corresponds to the extension you want to uninstall. .
Note: On Windows systems, another software installation may also add an extension that is installed to a location outside of the Mozilla installation directory. See the Windows Registry extension section below for more information.
Uninstalling an extension using Windows Control Panel
Another installed program may have added an extension to your Mozilla application. If you are unable to remove the extension using the Add-ons manager (see above) and you can't remove it from within the program's own settings, you may be able to remove it via the Windows Control Panel.
Control Panel list of installed programs
See if a separate entry for the add-on appears in the Windows Control Panel list of installed programs:
If a separate entry for the add-on doesn't exist, see if the program's entry includes the option to selectively remove individual components.
For example, CA (Computer Associates) Internet Security Suite 2008 includes the Website Inspector component, which adds the CA Link Advisor and CA Toolbar extensions in Firefox.  You can remove the CA Link Advisor and CA Toolbar extensions by removing the Website Inspector component from CA Internet Security, as shown here.
If entries for the removed add-ons remain in the Extensions list, exit your Mozilla application, open the profile folder and delete the files "extensions.cache", "extensions.ini", and "extensions.rdf".
Java Control Panel
On Windows, Java 6 Update 10 and above includes the Java Quick Starter (enabled by default in Windows 2000/XP) and installs the Java Quick Starter extension in Firefox. The uninstall button is not functional in the Firefox Add-on manager Extensions window because the extension is installed for all users via the Windows Registry (see below). To remove the Java Quick Starter extension you must first enable it in Firefox, if disabled ("Tools -> Add-ons -> Extensions -> Java Quick Starter -> Enable -> Restart Firefox") and then exit Firefox, open the Windows Control Panel, and double click Java. In the Java Control Panel, click the Advanced tab, click the + in front of Miscellaneous, clear the Java Quick Starter box and click OK.  
Windows Registry extension
Installing or updating certain software on Windows can register an extension for Firefox or Thunderbird. For example, a Windows Registry entry to install a Firefox extension can be added under one of these keys:
HKEY_CURRENT_USER\Software\Mozilla\Firefox\Extensions\ HKEY_LOCAL_MACHINE\Software\Mozilla\Firefox\Extensions\ HKEY_LOCAL_MACHINE\Software\Wow6432Node\Mozilla\Firefox\Extensions (Only on 64-bit versions of Windows)
The Registry entry name will be the ID name or GUID of the add-on and the value data will be the path to the folder containing the extension (see Adding Extensions using the Windows Registry - MDC for details). When Firefox or Thunderbird next starts, it will notice the entry and install the extension.
Extensions that are installed this way include the Java Quick Starter extension for Firefox (see above), the Microsoft .NET Framework Assistant   the RealPlayer Browser Record Plugin extension,  and the Lenovo ThinkVantage Password Manager extension for Firefox  . Although you can disable the extension in the Add-ons manager, the Uninstall option may not be functional (it will be "greyed out). In such cases, experienced users can uninstall the extension by removing the associated Registry entry and/or the contents of the folder containing the extension; otherwise, simply disable it.
Note: The program that installed the extension may include an option or preference setting to remove it. For example, the RealPlayer Browser Record Plugin extension can be removed from Firefox by opening RealPlayer, going to "Tools -> Preferences -> Download & Recording" and unchecking the option, "Enable Web Download & Recording".
There have been a few reports of malware being installed as a hidden Firefox extension, via the Windows Registry. In the reported cases, the
Starting in Firefox 3 and SeaMonkey 2, detected plugins are listed in the Add-ons window, accessible via "Tools -> Add-ons (or Add-on Manager) -> Plugins".   You can disable a plugin but you cannot uninstall plugins using the Add-on Manager. In many cases, browser plugins are included as part of a larger application, so you would normally just disable the plugin instead of uninstalling the entire application. For more information, see Issues related to plugins and PluginDoc.
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