Smart Max Tabs is a simple Firefox extension that does these:

• Set a maximum number of tabs opened in a window.
• Automatically close least used tabs, if maximum is exceeded.
• Save the automatically closed tabs in a searchable sidebar (From menu bar: View->Sidebar->closed tabs).
• Control and restrict oneself from opening too many tabs.
• Prevent tabs from overloading and overflowing the tab bar.

WARNING: There's a fatal bug in this public repo, I will come back to it when I have more time.

NOTE: This is a personal web extension that I use. If you think it is useful, star it so you can signal me that I should improve it and make it easily available for everyone.

This project was originally forked from another extension called max-tabs that only limits the maximum number of open tabs: https://github.com/kanru/max-tabs

MPL 2.0.