At pressing "Restore all" bad things happen:
- Locked tabs are lost;
- Some not-locked tabs are lost, too;
- Some tabs are re-open in new windows rather than new tabs;
Firefox 62 (64-bit)

After using it for months/years, I lost a whole lot of unrecoverable tabs.
With no warnings at all, yesterday it deleted all my tabs information and now I can't recover it :(
To quote another user: "Second time I am losing a whole lot of unrecoverable tabs.
And usually when I don't like something I just uninstall and move on with my life. But this time is different.
I feel like I have to WARN people because OneTab fails to do so. If you have a sub-par extension, either fix it(automatically backup? support recovery?), take it down or include a Disclaimer that your extension should be used only for casual usage.

Because anyone who actually wants to keep their sh*t should definitely STEER AWAY from this extension."

useless....

I lost all my tabs after launched this extension.

links' icons are broken.
If a lot of tabs saved, loading onetab page is slow.
It would possibly lost all of saved tabs.

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And now there's an better alternative (and is FREE SOFTWARE)(and don't require "Access your data for all websites").

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EDIT 12/24/2019:
Can't work on Firefox Android at all, all my opened tabs lost but only that poor 1 is saved!! If you can't do it, then don't make it available on Android platform!! What a garbage

It deleted all my tab information and now I can't recover it :(

Second time I am losing a whole lot of unrecoverable tabs.
And usually when I don't like something I just uninstall and move on with my life. But this time is different.
I feel like I have to WARN people because OneTab fails to do so. If you have a sub-par extension, either fix it(automatically backup? support recovery?), take it down or include a Disclaimer that your extension should be used only for casual usage.

Because anyone who actually wants to keep their sh*t should definitely STEER AWAY from this extension.

Update 2023-11-14 : I lost the entire OneTab content... several thousand URLs that I valued. 😔

Initial review :
Essential, perfectly effective, reliable, and ideally well designed!

This WAS absolutely great when it did what it was made for. Unfortunately, my onetab page has turned up empty and that means it isn't fit for its explicitly intended purpose.
Good idea, good attempt, but it's not worth trusting this add-on for anything more than casual usage.

Worst Add-on on Firefox (not necessarily applied to other browsers; maybe works well with others); it does not work at all; it won't budge a bit by reloading the expected one-page with all the tabs stacked.

Saves all Tabs in one window, kills all other windows without saving or even asking before closing them

Very useful addon but I have to uninstal it because it slowed down Firefox badly. What a pity. If it is fixed I would use it again.

OneTab is an extension to avoid. When it works it works great. Then you trust it. Then it lets you down.

Specific failure that I have seen several times: Several Firefox windows open with multiple tabs, go to OneTab Icon, Right click, OneTab->Send all tabs from all windows to OneTab. All windows disappear except for the OneTab window. Close out of Firefox, reopen. OneTab doesn't have those tabs that you just saved in it, neither does Firefox, you lose.

Great, until all your data disappears...

My laptop ran out of battery and stopped, crashing the system. When I rebooted, OneTab was empty. All my tab groupings? Gone forever.

What a pain.

I added 80 tabs to OneTab. After a moment, I clicked on Restore and everything disappeared. I do not have any tabs that have been open for about a year. They are not in the history of recently closed windows / tabs. They are nowhere. I lost a lot of valuable information for me :(

Broken. This is my favorite add-on but it has stopped working in a catastrophic manner and I just lost all of my tabs. The "bring all tabs into Onetab" function closes all the tabs and windows *but doesn't add them* to the one tab extension. It just threw away all of my tabs. This worked before firefox 57 and yes I am using the updated version. I even uninstalled, restarted, installed the latest version, purposely opened multiple windows with multiple tabs and tried again just to test it... only for it to fail again in the same way. Now I have to go through the history and manually find the 50+ tabs it trashed earlier and switch back to Chrome. They don't even show up under "recently closed". This add-on is essential to my workflow so Chrome is the only option now. tldr: Works perfectly for 1 window, fails epically at multi-window. Was a 5 star, now a 1.

Hasn't been working since the New Year. I tried removing and re-downloading it. I upgraded to the latest firefox today, and it's still not working.

I used OneTab for months! And now I find all my tabs lost. Without any crash. They're just missing and there's no recovery option. Sorry, this makes OneTab useless.

Just lost all my tabs after a crash. The OneTab list is totally empty. What a waste. Won't be using this again.