You can look at this extension *Hide Tab Bar With One Tab: https://addons.mozilla.org/firefox/addon/hide-tab-bar-with-one-tab/ ---- See also: *https://support.mozilla.org/kb/how-to-make-new-firefox-look-like-old-firefox *https://support.mozilla.org/kb/common-questions-after-updating-to-new-firefox *https://support.mozilla.org/kb/learn-more-about-the-design-of-new-firefox *http://forums.mozillazine.org/viewtopic.php?f=38&t=2824649