You want to hide the tab bar, or you want to limit each window to one tab, or both? Did you have this working in a previous version of Firefox and it stopped working, or have you had this issue for a while? ---- Regarding the '''tab bar''' this comment is from the Firefox 23 days: In Firefox 22 and earlier, you could suppress the tab bar when there was only one page open in the window, i.e., only a single tab. The developers are gearing up for a new interface, so removed that option. However, at least for now, you can restore it with an add-on: https://addons.mozilla.org/firefox/addon/hide-tab-bar-with-one-tab/ Note: I haven't tried it myself.