It seems that a number of vendors are silently installing Firefox extensions via registry settings. I would like to prevent Firefox from reading any Windows registry settings at start-up.

Does anyone know how to start up Firefox in a way that ignores Windows registry settings?

Is this a problem that Mozilla has solved by changing how Firefox loads extensions and/or uses the Windows registry?

  • 1
    Any real-life example of such extension? Or some references to articles on that?
    – Arjan
    Commented Oct 10, 2009 at 9:38
  • Back in Jun, Microsoft installed some .Net related extension which could not be uninstalled. Initially, it could not be disabled.
    – pcapademic
    Commented Jan 3, 2010 at 8:35

5 Answers 5


I don't know if there's an elegant solution to this, but you could go to the following keys:


... and simply adjust the Security permissions on them with Everyone - Deny... that would effectively prevent FireFox from reading its own registry settings, and other applications from writing to them, also.

Not sure what effect this would have on firefox's operation, though.


This doesn't directly answer your question, but if your ultimate goal is to prevent Firefox from modifying the registry you might consider running it in a sandbox. Sandboxie can run any application in a sandbox which prevents the program from modifying your registry or file system.


From the Mozilla help forum:

Firefox 3.6+ versions do prevent plugins from being installed to the \Program Files\Firefox\plugins folder to keep plugins out of Firefox, but that isn't how most plugins get "into Firefox". Firefox scans the Windows Registry for plugins that have the correct Registry key for Firefox, and uses those plugins from wherever thay are located on your hard drive. Once the program using that plugin is installed, and the Registry Key is set, all you can do is physically remove the plugin files or turn off the plugin in Tools > Addons > Plugins Sorry, I don't know how plugins are handled in Linux OS's. Impossible to prevent the programs you are installing from installing their plugins for Firefox. Once you give a program permission to install on your PC, it can do anything it wants with Firefox or any other program.


Im not 100% sure but I think portable Firefox doesn't mess around with the computer files.


  • Thank you for your response. Unfortunately, I have already tried Portable Apps version of Firefox. While they do implement a wrapper for Firefox, the Firefox binary is the same as normal, and that binary seems to accept the secret installed extensions just like the normal version does.
    – pcapademic
    Commented Jun 29, 2009 at 5:27

UPDATE I just read that extensions.ini is not important at all and is automatically generated. So I guess I am wrong here, also given the [HKEY_LOCAL_MACHINE\SOFTWARE\MozillaPlugins] key as mentioned by @routeNpingme. I'll remove this later today; just leaving it here to ensure others don't waste their time on the same thing.

Given the fact that Firefox allows for using different profiles, each with their own extensions, I never thought that it would use the registry as well. (Firefox being cross-platform makes me even wonder more about that, especially as Firefox already has it own kind of cross-platform mechanism of storing settings.)

So unless you're sure it's in the registry, you might want to peek into the Files and folders in the profile, especially extensions.ini.


Lists folders of installed extensions and themes.
The file is automatically generated by nsExtensionManager and is used by low-level code to detect chrome packages and XPCOM components provided by installed addons. Can be deleted to resolve various issues.

(See command line arguments to start Firefox with another profile.)

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