How To Access Hidden Firefox Preferences [MacRx]

This Might Void Your Warranty

This week a tip for Firefox power users. In addition to the Preferences accessible via the menubar, Firefox retains a comprehensive set of hidden settings that go back to it’s roots in the Netscape era.

Of course you are presented with an initial Caveat Emptor about the stability of your system and all that, but you’ve already jailbroken your iPhone and iPad (right?) so go ahead and dive right in…

Open up a new Firefox window or tab, and in the address bar type about:config, then hit Return.

How To Access Hidden Firefox Preferences [MacRx]

Current versions of Firefox present you with a “This might void your warranty!”  warning window (added to the program as of version 3 I believe); click the “I’ll be careful, I promise!” button to proceed.

You are now presented with a long list of obscurely named items.  These are the complete set of preferences for the program.  Some of these are items you can also set from the Firefox Preferences window, but most can only be tweaked from here.

How To Access Hidden Firefox Preferences [MacRx]

Scroll through the list to see the kinds of things you can control.  To narrow the displayed items you can enter text in the Filter bar, e.g., entering urlbar as the filter text shows only entries which control URL Bar behavior:

How To Access Hidden Firefox Preferences [MacRx]

Preferences listed as type boolean are true/false  values.  Double clicking on the Preference Name will toggle between the two states.  Any preferences which have been set to non-default values will display in bold in the list:

How To Access Hidden Firefox Preferences [MacRx]For items with integer or string values, double click on the Preference Name to bring up a window where you can enter the desired value:

How To Access Hidden Firefox Preferences [MacRx]

Some of these preferences are quite obscure.  Google the term “about:config” and the various preference names to find out more info about them.

Make note of a preference’s starting value before changing it, lest you get into trouble. It’s also a good idea to make a backup of your current preferences file (and other browser data) before making any changes.  You can find these items here (~ means your home directory):

~/Library/Application Support/Firefox      (this is a folder)
~/Library/Preferences/org.mozilla.firefox.plist

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About the author

Adam RosenAdam Rosen is an IT consultant specializing in Apple Macintosh systems new and old. He lives in Boston with two cats and too many possessions. In addition to membership in the Cult of Mac, Adam has written for Low End Mac and is curator of the Vintage Mac Museum. He also enjoys a good libation.

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