On Chrome and Safari (on Mac OS), command-shift-N opens a new incognito/private window. And so sometimes when I want to open a private window on Firefox I used command-shift-N by mistake (when I should have used command-shift-P). On Firefox, command-shift-N reopens the most recently closed window, and quite often I had a lot of tabs in the window I last closed and Firefox would try to open all of them. This is kind of annoying.

Because of this I want to disable Recently Closed Windows or change its short cut key. I have tried the Menu Wizard add-on, but it doesn't seem to find this menu item. I assume that it's because it's dynamically created. Is there a way to do this?


There's an addon available for Firefox that lets you change the shortcuts to whatever you want. It's called Customizable Shortcuts:


Run the .xpi file:


  • Thanks! This works, but you have to change the menu item "Undo Close Window", which is not shown in the actual menu. After changing the shortcut setting and restart Firefox, if you command-shift-N, Firefox now only flashes the menu bar once (weird) and would not open the old window. – ceiling cat Jun 14 '15 at 15:49
  1. Enter about:config and hit Enter
  2. Search browser.sessionstore.max_windows_undo
  3. Set the value to 0

However, setting a new keyboard combo for "New Private Window" in the macOS System Preferences only flashes the menu and nothing happens.

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