How to remove unused preferences from Firefox’s about:config page

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Many extensions that you install in Firefox add one or multiple preferences to the browser to control various settings.

Problem is, these preferences are not removed when you uninstall the add-ons again in the browser. If you never clean up the configuration of Firefox, you will end up with a bloated file that contains lots of unused preferences.

Apart from extensions, old preferences not used in Firefox may also add to that provided that you have customized their values.

While you can delete preferences manually by editing the prefs.js file that you find in the user profile folder, or by installing an add-on that does that for you, you may also delete unused preferences directly on about:config.

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If you open about:config in Firefox you will notice that the page offers no direct option to delete preferences on it.

The right-click context menu shows no delete option and tapping on the Delete key on the keyboard (with or without modifiers) does not remove preferences as well.

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What most Firefox don’t know is that it is possible to delete preferences, albeit indirectly.

To remove unused preferences from Firefox, right-click on them and select reset from the context menu. Once you are done resetting all preferences that are not used anymore, restart the browser.

When you open the about:config page again, you will notice that the preferences have been removed from Firefox.

The procedure may take some time as you cannot select multiple preferences in one go. This means that you have to repeat the select, right-click, reset process over and over again until you have reset all unused preferences you want removed from the browser.

It may still be faster to edit the prefs.js file in the user profile folder as you can edit it in a regular text editor on your system that allows you to remove multiple lines in one go.

One of the advantages of using reset on the about:config page is that you can be sure that only unneeded preferences are removed from Firefox.

Now You: Have you removed preferences from Firefox in the past?


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How to remove unused preferences from Firefox’s about:config page


Martin Brinkmann


Find out how to remove unused preferences from Firefox from its about:config page directly.

About Martin Brinkmann

Martin Brinkmann is a journalist from Germany who founded Ghacks Technology News Back in 2005. He is passionate about all things tech and knows the Internet and computers like the back of his hand. You can follow Martin on Facebook, Twitter or Google+

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