Exactly what I was looking for! I use multiple windows to keep my tabs somewhat organized by task, but it can get a bit overwhelming remembering what tab I was on in what window. Being able to title the window solves this issue perfectly. It even remembers the window title after I've quit and relaunched Firefox.

The only change I might suggest is disabling the tab title, allowing only the window title to be displayed.

Rarely does one find add-ons or extensions that become so integral to one's workflow that it makes it hard to use other browsers. For me, this is one of those add-ons. If you like to organize your tabs around tasks, topics, or projects, this add-on in indispensable in being able to quickly task-shift within a browser. It's interface clean, easy to use, simple to understand and customizable. It also plays nicely with containers for the ultimate in separation of concerns. Thank you, Tomasz, for creating it; it's very handy.

This is a great add-on for complex setups.

I'm using a pathological number of FF windows, scatter among 12 desktops for various topics. It helps me to organize and manage this state better than ever.

While at it, and since I suffer from a session store issue of FF https://bugzilla.mozilla.org/show_bug.cgi?id=372650 since a long time, I created a small tool, that allows me to store and restore the FF session state using the static titles of this add-on:
https://github.com/frispete/wm-win-tool
https://pypi.org/project/wm-win-tool
Thank you, Tomasz.

Perfect with a window manager that can move windows to another workspace based on window title!

Wonderful, as I organize my windows by topic, now when I click on firefox icon in my (Windows) taskbar, I can see the topic the extension lets me set! Without the extension, the Firefox window titles are just the last tab's title, and it was impossible to quickly find, for example, my "email" window, or my "travel planning" window if I'd gotten, say, wikipedia open in both windows.

Thank you!

Simple and great! I put spaces around my tab names to provide a little more space within the brackets it uses; i wish it would give just one space between the closing bracket and the tab name.

Tip: Use with https://addons.mozilla.org/en-US/firefox/addon/tab-mover/ and all your tab organization needs are taken care of, without the bugginess all the tab group plugins seem to have.

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.