Press Alt+Shift+D to duplicate the current tab (Option+Shift+D on Mac). Shortcut is configurable.
There are additional shortcuts as well. You can configure and use all of them at the same time.
- There is a shortcut to open the new tab in a new window.
- There is a shortcut to pop the current tab (or multiple highlighted tabs) out to a new window.
- There is a shortcut to open a blank new tab to the immediate right of the current tab (i.e. instead of all the way to the right).
Tip: Even without this extension, it is possible to middle click the refresh button to duplicate the current tab.
Firefox version: https://addons.mozilla.org/addon/duplicate-tab-shortcut/
Source code: https://github.com/stefansundin/duplicate-tab