Does exactly what it says on the tin. This is an incredibly basic organization feature that somehow has been missing from life for a long while. Most addons rename tabs or change the naming scheme of the window title, which isn't very useful for per window organization. I separate my tabs per topic in different windows and I go back and forth a lot and having an addon like this helps find things faster.

The only thing I could call a quirk is that if the window's current tab is a new empty tab, the prefix will not appear and the window will simply be "Mozilla Firefox".

PUTS A PREFIX in the titlebar - EASILY VISIBLE IN TASK SWITCHERS (just use ALL CAPS!!)

I use this to delineate firefox profiles. Better than the addons specifically designed to do so for 1. permissions required and 2. implementation

Do the job

an invaluable plugin for those who frequently use many firefox instances simultaneously.

Eager to use but cannot download due to "network error" (but I am indeed online).