Configuring Firefox proxy settings for all users

Spread Firefox Affiliate ButtonI recently had an issue with the latest version of Firefox (v3.6.15). Normally, when we install Firefox on our network, we have to change the proxy settings from the default “No Proxy” to “Auto-detect proxy settings for this network”. This doesn’t normally cause much of an issue as we only use Firefox on a few select machines and can be changed by the individual user. However, it seems the default install behaviour has slightly changed to add a new option that seems to muddy the water. There is now a “Use system proxy settings” option (similar to Google’s Chrome) that seems to be selected by default for new users. Although this may seem to make sense, on our network this causes terribly slow page load times, e.g. 10 minutes to load Luckily I found a way to set the “Auto-detect” option for all users.

WARNING: This seems to have changed again since Firefox 4 was released. If anyone knows how to change it please add a comment.

It turns out Firefox now stores this kind of configuration in the all.js file, located in the Firefox install directory (e.g. “C:\Program Files\Mozilla Firefox\greprefs\all.js”). To change the default proxy type do the following

  • Open Notepad.exe (run as admin to allow you to save any changes)
  • Open the all.js file
  • Search the file (CTRL+F) to find the network.proxy.type setting
  • Change the number to relate to the correct setting. MozillaZine explains the possible values
    • 0 = Direct connection, no proxy. (Default in Windows and Mac pre-Firefox 3.6.4)
    • 1 = Manual proxy configuration.
    • 2 = Proxy auto-configuration (PAC).
    • 4 = Auto-detect proxy settings.
    • 5 = Use system proxy settings. (Default in Linux; default for all platforms, starting in Firefox 3.6.4)
  • Save the file.
screenshot of firefox all.js file in notepad
Change the proxy settings in the all.js file

This should now work for any new user that logs on to the machine. If a user has already used Firefox you will need to change the same setting in their local profile (e.g.  “C:\Users\%USERNAME%\AppData\Roaming\Mozilla\Firefox\Profilesqwi49jb.default\prefs.js”).

If you would like to change this setting domain wide I would recommend using Group Policy Preferences to update the file remotely on the relevant workstations.

This all.js file holds a lot of other settings for Firefox (it has over 1700 lines) and I will probably be coming back to this for other customizations of the web browser. It would be great if Firefox provided ADMX group policy templates for this kind of thing but as far as I’m aware that project died out a few years ago (which puts it at a severe disadvantage to Internet Explorer or Google Chrome). Have you used this file before? What tweaks have you made to help configure Firefox for multi-user networks?

4 thoughts on “Configuring Firefox proxy settings for all users

    1. Thanks. I couldn’t tell you what version of WPAD we are using. It was all set up by our Linux guy who has moved on to greener pastures.
      Worth looking into though. Thanks for the link.


  1. “WARNING: This seems to have changed again since Firefox 4 was released. If anyone knows how to change it please add a comment.”
    We found a file under Mozilla Firefox\defaults\pref\channel-prefs.js
    We added there the “pref(…” lines needed and it worked.
    eg.pref(“general.config.filename”, “mozilla.cfg”);
    for specifying a configuration file for locking the proxy settings of Firefox 4


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