This is a simple browser extension that lets you know the amount of tabs you have open. The code is very lightweight and only runs on-demand, when you click the extension's icon.
Inspired by my answer to this superuser SE question superuser.com/questions/967064
Do with this code as you wish, as long as you don't blame me.
This extension supports both Manifest v2 (Firefox) and Manifest v3 (Chrome, Safari) formats.
Before releasing, duplicate/rename the appropriate manifest file to manifest.json. The only files
required in the final bundle are:
icons/
js/
manifest.json