I found the almost perfect replacement for Firefox's (before v.57) TabGroups. OneTab fully closes the tabs and reloads the websites on restoring the tab. However, if this is what you need, OneTab works wonderfully.

I have Firefox Multi-Account Containers. When I collapse all tabs on different containers, when restored, they don't return to the original container.

Great! Thanks!

TOP top top. Permets de faire le ménage rapidement dans les onglets ouvert sans pour autant les perdre si saturé le menu des raccourcis surtout lorsque l'on aime nettoyer l'historique régulièrement.

I often have a ton of tabs open, which slows down my browser and makes it difficult to be effective in my research. One Tab is THE BEST. When I have a bunch of tabs open that I want to save but don't want to bookmark, I just hit one tab. All of my open tabs are now in a list. Easy to search. You can easily reopen one or all of the tabs, delete one or more tabs. Makes my life so much easier.

Great addon. Could you please add an option to display OneTab in the tab I'm already using, instead of opening another tab for it?

noticed a bug, file:/// links are saved, but as soon they are opened they are removed and not opened...can't contact anywhere except here...will give higher rating if bug is fixed

Cannot get it to work. Can't open xpi file to even try. Needs to be more user friendly.

Все отлично работает. Не хватает горячих клавиш.

Je sais pas ci il est bon ou pas je vient juste de l' installe. Merci

I tend to open a lot of tabs. Many tabs. I think I have the attention span of a flea. One tab helps me save them all in one place where it's easy for me to refer to them. I guess I am a tab hoarder but I do a lot of research for myself and my writing and One Tab allows me to easily access all that fun without keeping all the tabs open (and thereby slowing down my computer). :) Great stuff. You need this addon!

10-10-24: still good not perfect but pretty good.
aug, 2024: it's gotten much better. Recommended
Sept 2022: It's gotten better but the thing that remains that is really annoying is that it won't load the saved urls automatically and you have to disable and re-enable it to get the saved urls to load. The problem with the auto opening of the tabs has been resolved in their settings, so that is not an issue now. But I am sick and tired of having to disable and re-enable it to get it to load on command. I dont' want AUTO load but I do want them to load when I issue the command.

June, 2022: It's gotten better, easier to use. On some browsers such as epic, it will not auto activate and you have to disable and reenable to get it to show. Need a better way to save the tabs when it goes haywire. Should have an auto setting to automatically lock the tabs.
Nov 10, 2021:
Demoted this add on to ONE STAR.
It acts like trojan or malware and opens a second FFOX window without user input and with setting set to open tab only, ignores the setting and opens a new window. Reported as malware.
mostly disabled it. Breaks Loads whether you ask it to or not and then breaks your vpn or music connection in doing so. Seems pretty obvious they are messing with your other browsing connections. It's only good for one thing, that is if you have to open many URLS and don't want to bother pressing the keys to make a book mark. I consider this spyware. Don't know why mozilla recommends it, but they must have low standards.

Easy to use and get used to. Though, I wish it had a dark mode setting.