Sometimes we accidentally close a tab in Firefox we didn’t mean to close. Instead of looking the website we want in the History, you can do this trick to reopen the last closed tab.
If you accidentally close a tab, you just need to press “Ctrl + Shift + T“. And the last closed tab will be reopened in your Firefox.
Try it. Open a new tab, close the tab and press “Ctrl + Shift + T”. Very helpful huh? 
Edit: You also can open last closed tab from History > Recently Closed Tabs. Thanks to Izzat for this tip. 
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gee.. thanks! very helpful
or you can click history tabs > recently closed tabs
simply middle click in the empty part of the tab bar u will see ur recently closed tabs in the order it was closed.but i think it works if u have ‘tab clicking options’ extension installed.
Instead of using 3 buttons you can simply do this by pressing 2 buttons. Ctrl + F12
Keith
Doesn’t work for me :\
you are welcome.
but there is no empty space in my firefox tab.
doesn’t work for me too.
cool… thank you.