Being one of the popular web browsers in used worldwide, Mozilla Firefox offers users a fully customizable way for web surfing. Besides a wide range of addon apps for users to enhance its functionalities, another beauty of this browser is the flexibility to modify the application settings (known as preferences) for better performance. Many users probably are not aware that the Firefox browser hides many of the preferences in the pref.js and user.js files which are located in the Firefox profile folder. Users will not be able to access and modify these preferences by opening up the regular Options or Preferences dialog interface. To edit or modify these hidden preferences, one of the ways is via about:config hack. By making changes to these preferences, users can customize the browser for a more handy use.

To make changes to hidden preference via about:config, users need to type about:config in the Location Bar (address bar) and press Enter to display the list of preferences, as shown below. Users will be prompted with a warning message: “This might void your warranty! Changing these advanced settings can be harmful to the stability, security, and performance of this application. You should only continue if you are sure of what you are doing.” Click the button labeled “I’ll be careful, I promise!” to continue.


From the list of preferences shown, users can easily modify the value by double-clicking the preference.


My Digital Life has recommended a number of preferences modifications via about:config hack in our previous posts and they are compiled here again for users’ reference: