Tab Stats

This add-on quickly shows some interesting statistics about tabs. For example, the total open count, including inactive tabs. It also shows breakdown by hostname, protocol, and addresses (which is useful because you might have multiple tabs open to the same address without knowing it). Since I use Dark Mode and Firefox is set to follow the system theme, I had trouble seeing the icon at first because it is just a black silhouette of a tab. So for future users: this add-on installs a button to the right of the drop-down menu which is itself to the right of the tabs and to the left of the minimize button (at least on Windows). I used Customize to move it next to my normal add-on buttons.

Simple but awesome for dealing with duplicate tabs, closing all tabs from a site (bugzilla...), counting tabs and loaded tabs. I've been using it for years (I have 10000 tabs currently)