Do you have the Navigation Toolbar visible with the "3-bar" Firefox menu button or the Menu bar and access the File menu via "Alt+F" ? Are you sure that you didn't switch to Full Screen mode ? Make sure Firefox isn't set to run in Full Screen mode (press F11 or Fn + F11 to toggle; Mac: Command+Shift+F). *https://support.mozilla.org/en-US/kb/how-make-firefox-and-websites-go-full-screen When you are in Full Screen mode, hover the mouse to the top of the screen to make the Navigation Toolbar and Tab bar appear. Right-click empty space on a toolbar to find "Exit Full Screen mode" and "Hide toolbars". You can use one of these to leave Full Screen mode: *press the F11 key *click the Maximize button at the right end of the Tab bar *click the Full Screen button in the "3-bar" Firefox menu button drop-down list