I was really bummed when TabGroups by Quicksaver was decommissioned with the upgrade to Firefox 57. Loved that extension. I remained that way when I installed SyncTabGroups by Morikko. It was not really intuitive and I ended up with all of these groups I didn't need. A bit of a mess. HOWEVER, with the developer's last update (Feb 2018), this has become a first rate extension for all of us who love our tabs and want to keep them organized. Many great setting features - able to turn on and off most features depending on preference. What I love is the ability to see how many tabs I have open and which groups they are in. Firefox really slows down and eventually becomes unresponsive if too may tabs are open. One can also used the pull down arrow in the menu to see what tabs are in the group and delete them from the menu. And I also love the one can search and find a tab in the menu. Saves the frustration of hunting for tabs among the groups. I love that the developer added the name of the group to the Firefox window icon so I can easily switch to the window based on what group I would love to work on. Hoping the next version will put the name on the open window itself so I can easily know which group I am working on based on the open window. I also love that one now can move the tab from one group to another with just a right click of the tab. Now that I have been working with the extension awhile, I am actually preferring that the tab groups are based on the window instead of group tabs (I believe that is how TabGroups worked?) . A cleaner way to work. Finally, when I initially installed SyncTabGroups, I had questions. The developer was very responsive. Great customer support. I highly recommend giving this latest version of the SyncTabGroups extension a try.