Click the “Remove” button, and the extension will be removed from Firefox completely. After that, you’ll see a confirmation window appear. If your Firefox extension has an icon in the toolbar, you can uninstall the extension quickly by right-clicking the icon and selecting “Remove Extension” from the menu that pops up. However, Firefox does have additional library files that aren't removed when you delete Firefox.app. OS X Yosemite doesn't have a complicated uninstall application. Like most apps, uninstalling Firefox from an Apple computer is a simple matter of deleting the application file. You can use the information in this article as a general guide. You should set another default browser if you are not going to reinstall Firefox and it is currently the default. This article contains instructions to uninstall Firefox and remove it from your system.