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What are the "default" config settings (about:config)?

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Is there a default config file somewhere? I have installed / uninstalled many extensions over the months. I don't really want to rebuild my FF install. I was wondering if there is an "out-of-the-box" default config file I could compare to my current config file. Thanks.

Is there a default config file somewhere? I have installed / uninstalled many extensions over the months. I don't really want to rebuild my FF install. I was wondering if there is an "out-of-the-box" default config file I could compare to my current config file. Thanks.

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There is no default config file.
Firefox stores the values of prefs that have been modified (i.e. show as user set) in the prefs.js file in the Firefox profile folder.

You can use this button to go to the currently used Firefox profile folder:

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If you want to reset a modified preference to its default value, right-click it and choose Reset. Reset preferences that normally don't exist (like those added by extensions) will be removed after restarting Firefox.

Firefox only keeps track of modified preferences in the prefs.js file in your profile folder. If you rename this file while Firefox is closed, you'd start over with the default set of preferences (though any add-ons you have installed would create preferences again once Firefox is restarted). It's also possible to set preferences at startup in user.js, or to lock them for all users.

If you want to see what preferences look like when first starting Firefox, you can start Firefox in a new profile.