Brilliant as always (kudos xtrm_xtrm!!) but needs maintenance - new bug to fix with v21? Rated 3 out of 5 stars
The version in xtrm_xtrm's profile (see Dr. Zev's comment May 15, 2013) works with v21, but there are still issues with tabs being restored in the wrong order and suspended groups "lost". These are well known, and I can confirm that going back to FF18.02 (or perhaps 19) solves them. But it highlights the need to pick this code up again!
Quick pro tip - if tab groups lose sync with Pano (extension) or panorama, or other extensions using groups, then zapping out briefly to Panorama view (ctrl-shift-E) and back ([X]) seems to resync Panorama's internal tab groups database nicely.
User tip (increased performance) Rated 5 out of 5 stars
Update to my review - heavy tab users might also want to look at "Suspend background tabs" which I found worked very well with TGM to increase responsiveness and memory use nicely.
See my review of that extension.
One of very few essential "superb design" add-ons for serious browser use, and one of the first I install. Rated 5 out of 5 stars
Been using this for 3 years, time to update my review.
Superb. One of my (few) "Do Not Browse Without It" add-ons. Allows you to do everything very neatly, and (Firefox 12-16) bug free as near as I can tell on any big stuff. Drag drop, Hibernate, Suspend, Reorder, AutoBackup, Versatile, and yet not obtrusive.
No slowdown even on huge sessions (tested on 1000+ tab use to give an idea).
What I use it for:
I can have a "group" bar of "projects or jobs I'm doing" and keep all tabs on one project together, suspend when not working on it, resume when I want to, and it's right there on my browser where I naturally look for it.
Brilliant - please take this as great thanks!
One request - any chance of an option for the group bar on the left or right, as well as top/bottom? Would allow far more groups to be visible and better managed? :)
Essential extension - rely on it completely. Superb. Rated 5 out of 5 stars
Allows you to create a second bar containing tab groups. Immensely configurable, very very powerful - keep all tasks in separate groups and switch between them. Suspend groups for memory saving, or drop them to a "hibernated" list for later retrieval. Full drag and drop - everything. If a heavy tab user this extension will change your life.
Main point is, it will need configuring. The current tab color, read and unread tabs, when to open a new group and whether to automatically prompt to rename it, session backup options.... expect to play with these, but once you find the setup that works for you, it's a game-changer. I use it with Tab Mix Plus and Vertical Tabs and they're all compatible.