Firefox is truly a very customizable browser. It has lots of hidden features and options which are not accessible via the browser's preferences UI. Add-ons enable many of these features to be customized in a user friendly way. Others can be tweaked with the built-in configuration editor (about:config). One such secret feature of Firefox is the ability to change the icon of the main window and bookmarks as well as library windows. You can even set your own icon for the downloads library, the bookmarks window, and the view source tool without using any third party tools. Let's see how it can be done.
Modern versions of Firefox have a built-in, native option to define user-specified icons for most of its window types. We can use this feature to customize Firefox icons.
Right click the Firefox icon on your desktop and choose 'Open file location' to open the File Explorer application right at the Firefox installation folder path:
Here you can see the 'browser' folder. Open it and create the 'chrome' subfolder. Note that you might get a UAC confirmation request. Just allow it:
Inside the chrome folder, create an 'icons' subfolder. Again, approve the UAC request by clicking Continue. After that, create a 'default' subfolder inside the icons folder. You should achieve the following path:
C:\Program Files (x86)\Mozilla Firefox\browser\chrome\icons\default
Put icons which have the following names inside the 'default' folder you create above:
- main-window.ico - an icon file for the main window
- downloadManager.ico - an icon for the downloads library window
- viewSource.ico - an icon for the 'View Source' tool window
- places.ico - this icon will be used for the 'Bookmarks' window
- printPageSetupDialog.ico - this icon will be used for the print setup window
- Wizard.ico - this icon is used for the various settings wizards, i.e. Setup Sync wizard. Note that this icon will be displayed only in the taskbar, since the Setup Sync window does not have any icon in the title.
- BrowserPreferences.ico - this icon will be used for browser preferences and also will be displayed only in the taskbar
- default.ico - this icon file is used in case the browser displays some window without a defined icon, i.e. a window from some add-on. Note that many add-ons have an icon defined. For example, the popular Tab Mix Plus add-on uses the following icon file for its preferences window: TabMIxPreferences.ico.
- CustomizeToolbarWindow.ico - this icon is used for the customization preferences of toolbars.
- unknownContentType.ico - this icon is used for the 'Opening...' dialog.
- openLocation.ico - this icon is used for a special dialog box which appears on the screen only if you have removed the location text field from the navigation toolbar.
Let's place some colorful icons in our 'default' folder to see these customizations in action. I will use the following icons: