Mass Deploying Firefox Preferences for Mac OS X

April 24th, 2009 by Charles Edge

Firefox has a number of preferences.  Not all are available in the GUI.  To access these preferences, you can simply open Firefox and type the following in the address bar:

about: config

This will allow you to customize preferences, whether or not they’re otherwise known, line by line.  These can then be copied between users, by inserting lines into the preferences file.

Like with most applications on Mac OS X, the preferences for Firefox can be deployed en masse.  It is a bit more complicated than deploying preferences for some other applications.  The reason for this is that the path to the preference file isn’t the same for all users.  The file is located in the ~/Library/Application Support/Firefox/Profiles directory.  It is an 8 character string followed by .default.  For example, lzwntwo9.default.  In this folder is a file called prefs.js, which contains all of the preferences for Firefox.  For example, the following line will disable the check for whether you wish Firefox to be the default web browser for a user:

user_pref(“”, false);

Once you know what preferences you’d like to push out there are two options to do so (there might be more, but these are the two we’ve used):

  • The first is to edit items in the bundle.  Most of these can be edited using the /Applications/ file, although the home page will be set using the /Applications/ file.  One note is that when you go to customize the prefs.js file it will give you a fairly nasty warning, but then it will push changes out to new accounts; however, don’t make any changes while the application is open.  Additionally, this method requires deleting the existing preferences, so if you simply want to push out updates you’ll need to resort to the second method.
  • For the second method, we look at a script that finds the name of the directory located in ~/Library/Application Support/Firefox/Profiles for the user (or all users for computer-based policies) of the system.  We then set that as a variable.  For example, using the output of ls ~/Library/Application\ Support/Firefox/Profiles/ as a variable called FFPREFSFOLDER would then be used to alter the contents of the js file using ls ~/Library/Application\ Support/Firefox/Profiles/$FFPREFSFOLDER/prefs.js as the actual path of the file for a user.

Now you can insert (or replace) the line that makes up the specific preference.  This isn’t nearly as clean as using defaults to push out Safari preferences.  But it does provide a way to push out Firefox preferences, be it as a file drop to replace the preferences in the application bundle or as a line edit to alter settings of an existing users browser.

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