tabsleeper per Tabsleeper

Tabsleeper lets you sleep Firefox windows and tabs, putting them somewhere safe and closing the window. When you’re ready, you can wake them and pick up exactly where you left off.

It will ease the load on your computer, saving battery, and making it faster overall. You can manage different sessions, keeping your browsing tidy and organised. Plus, everything is saved locally so it’s private.

Never again get frustrated by tab overload. Sleep it away and you can always come back to it later. Or not.