Mozilla Firefox has a really nice feature enabled by default. Firefox warns you when you press the close button while you have multiple tabs open. The feature is really useful against accidental presses on the close button. It is very useful to me personally as I have accidentally lost work in other browsers during several occasions.
For those who do not need such a feature, Firefox gives a checkbox at the confirmation (Exit and close tabs?) dialog – “Warn me when I attempt to close multiple tabs”. Now, if you use the feature and you have accidentally disabled it, then here’s how to get it back.
Open Firefox Settings: Click on the hamburger button () and then click on Options.
Under the Tabs heading, check the box before “Warn you when closing multiple tabs”.
That’s it! Your useful confirmation is back and will warn you when you try to close Firefox with multiple tabs open.