The latest update requires to disable and reenable the extension to have it working properly.

Update broke OneTab. Going back to previous version.

This was an indispensable add-on for me until today (16 Sept. 2020). Today's update (v 1.36) has broken OneTab completely. I can no longer save tabs, nor can I get the OneTab page to open. I am using Firefox 80.0.1 running under Windows 8.1 Pro x64.
I was able to revert to v1.29 (which still works) on a Windows PC, but only by first removing and then re-adding OneTab, which resulted in the loss of all of my stored tabs. The instructions at https://www.one-tab.com/firefoxRestore are evidently outdated, as the indicated "simple-storage" folder under Windows 8.1 Pro x64 is empty, regardless of whether Firefox is running.
Having learned from my experience with the Windows PC, I disabled updates on my Ubuntu PC. This appeared at first to have the desired effect. However, when I started Firefox again after rebooting the system, OneTab was missing completely. I haven't found any instructions for recovering lost tabs under Ubuntu.
I have made exports of saved tabs on both machines, but they are a few weeks old. OneTab doesn't appear to have an automatic backup facility, and since it is unclear where its data now resides, I see no way to implement one.
Update: OneTab is working again as of th e new version, 1.39 (see developer response below), so I am upgrading my rating to 4 stars. I especially applaud OneTab's efforts to require the minimum permissions needed, although I would caution users to check the setting for reading tabs in private sessions, which is enabled by default.
The add-in is so useful that I would give it five stars, if:
1. The instructions at https://www.one-tab.com/firefoxRestore were updated. In case anyone is interested, OneTab appears to now store its data in an SQLite db in a folder named "idb" under \storage\default\moz-extension+++1297484c-254f-45f9-a970-69c5c1cc0f50^userContextId=4294967295
2. It would add an automatic backup/export feature. The HTML export/import works very well. How much trouble would it be to automatically store the export file? This could be an option to be done on each update of the list.
Judging by the posts my web search turned up, this isn't the first time a bug has caused OneTab users to lose data. Regardless of the problem's source, I am sure that many users would be glad of some such insurance.

Amazing

Great Add-On. I have a couple recommendations for the developers, but they're too good to mention here.

Excellent!

I created the account specifically to write this review. I downloaded OneTab to get rid of old and redundant tabs that I had left open. After it succesfully merged them all in one tab, I proceeded to delete the unused ones. After restoring the session my firefox froze and when I opened it up again literally all my tabs were gone.
For many years a lot of people were telling me that I would be better off using using bookmarks more and I think OneTab is all I needed to make me switch.

this extension is a life saver wish i had found it earlier.

>>> UPDATE REQUIRED TO FIX FIREFOX ISSUE ON ANDROID!!! <<< ### DO NOT INSTALL!!! UPDATED JULY 2019!!! ###

This is a must have for researchers, snoopers and the average brained investigator. This extension allows you to categorize what you've been searching, title the bundle in a nice little list, save, lock, create a webpage for sharing and edit. It takes some practice to manage the finger skills and proper drop downs to get your first collection just right. So, play with it while you create your first collection all in OneTab.