For those who have lost tabs, I discovered that selecting Exit from the hamburger menu instead of X (close) avoided loss of tabs. Also, if X is clicked by mistake, I found that restarting my laptop (or possibly just closing Firefox and reopening it, I'm not sure) restored the tabs I had open.

When first opening Firefox, a succession of several sessions, one with only 1 tab and others with a group of tabs, rapidly appear before displaying just one session with the right group of tabs. I'm now going to disable this add-on and stick with Firefox's "open previous windows and tabs" option.

Edit: The behaviour above (2nd paragraph) still happens even after disabling the add-on, both with X (close) and Exit. AND this edit paragraph is missing (despite definitely clicking Update review) if closing with X!!

Mod strongly discouraged.
I usually set my windows or tabs using firefox bookmarks and it works fine.
But Onetab when it opens them again the tabs are all UPDATED AT THE SAME TIME!!!!
As a result, I reopened a window with 70 tabs and they were all updating 1 by 1 and loading all 70 at the same time, instead of doing what bookmarks do and putting them on hold.
So it took 20 m and crashed.
Fortunately, I was able to get other windows, the one it hadn't tried to open or the one where I'd put a lock... but when I relaunched the one that was loading, I had 6 tabs out of 70 ... lost forever ...

Doesn't even show on the addons bar, tried restarting but to no avail. Sad.

AVOID IT! All this extension will mostly end up doing is causing loss. It is known to randomly or unanticipatedly lose all or data. You have been warned.

This extension did not do what it says. Took control of my browser and would not give back control until I uninstalled it. It still did not uninstall completely and has its own icon in the top left corner of my browser instead of Firefox icon. Hosed my tabs and lost my data. Had to restore my session by restoring one tab at a time from my history. TOTAL GARBAGE

it works until it doesn't. And when it doesn't, it makes you lose all the tabs that you just saved. I lost over 50+ tabs because it just stop working.

Great idea but I can't get it to work as described

Used to be great and really reliable, but more recently, it has really sucked, having lost my entire list of tabs several times now. A shame because it was really great when working as it should. But given I had important stuff I needed to come back to in those tab lists... yeah, not happy. Just glad I've been a little deficient in clearing out my history in the last couple of months, so most of those links are at least somewhere.

Installed, clicked it, lost 100 open tabs.

ADD-ON IS BROKEN!

Lost my tabs two times in a row now..

Author kill youself! WTF where is easy ability transform all the pages from one to many?? I los a lot of time with you raw stupid app.

纯纯垃圾

It doesn't open anymore

這是一個簡單易用的好東西，
直到Firefox大更新前都是。
今天大更新後，我的資料被清空了，
嘗試許久也救不回來，
是時候，該放棄這套工具了。

這套工具幫助了我許多年，
還是謝謝你作者。

No cloud or sync

All of my saved pages randomly disappeared.

Não pede confirmação para remover todas abas atuais, para agrupar em uma aba/página com os links. Deveria ter essa opção de configuração, inclusive a confirmação para realizar esse processo de agrupar os links de abas em apenas uma aba DESTACANDO que as abas serão fechadas.

DO NOT INSTALL THIS. It will delete all of your tabs, with no way to recover them. Check the other reviews, this is happening to everyone.

Don't use it, it's very great at first and then it will lose all your tabs. Twice.

Has worked well until recently, but now all my tabs are gone and I see I'm not the only one..oh, and their instructions for recovering lost tabs is a joke.