Adds toolbar buttons for quick access to undo the closing of tabs. The button has two modes depending on what setting is selected. It either simply reopens the most recently closed tab. Or it can show a list of recently closed tabs so you can pick which one to open again. The number of tabs in this list is configurable. None of this is really new functionality. You can undo closing a tab with Ctrl + Shift + T or from the tab context menu. And the menu is already exists under History > Recently Closed Tabs. This extension just makes it faster to get at. For those asking for the old multi-function button back: Make sure you set this button so it does not show the drop down (the default setting, so change it back if you modified it). Then install Close Tab History Button and put it next this one. That is the closest I can get you to the old behavior for now. I am working on a patch for Firefox so that the possibility of doing this will come back. Consider installing this button's greatest rival the Close Tab Button. I am looking for translations for this extension if you are interested in helping check out the project on crowdin. This is part of a set of tab related buttons: Reload All Tabs Button, Stop All Button, Tabs List Button, Close All Tabs Button, Copy Tab Button, Reload Skip Cache Button, Undo Close Tab Button, Close tabs to the right Button and Close Other Tabs Button. The extension is part of the Toolbar Buttons project and is built with the MozButton SDK. Follow us on Twitter, or get involved on GitHub. If you have ideas for new features we are more then happy to consider them for the next release. Just leave a comment, or better post to our Forums