You'll need a custom userChrome.css @namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* to hide the native tabs */

You'll need a custom userChrome.css @namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* to hide the native tabs */ #TabsToolbar { visibility: collapse; } /* to hide the sidebar header */ #sidebar-header { visibility: collapse; } You probably want to enable the menu bar if you do this, to stop the minimize/maximize/close buttons from overlapping the menu & other buttons on the right top corner.