Right now this add-on is unstable or bugged. The icon disappeared from Firefox and I couldn't use it, so I had to reinstall it to work again. Which resulted in losing all my previous tabs!
I hope this issue gets fixed soon.

It broke on the recent Sept 2020 update, but following a suggestion to turn it off and on again under about:addons page actually fixed it. I've been using this for a few years and continue to love it despite this.

Used to be great but now every time I open Firefox I have to go an manage my extensions turn it off then turn it on again. I don't know if this is the team's issue or a firefox issue, all I know is it is very irksome and I would like to hope it gets resolved

To those who also want to give 1 star review: addon now requires turning it off and on to start working again for some reason. Unforseen update of Firefox?

The add-on simply stopped working few days ago. No instructions whatsoever on how to recover tabs on a Linux machine of course... In short: all the tabs lost!

EDIT: Changed from 1 star to 5 stars
The add-on is working again, and all the old data reappeared. I guess problems happen, the important thing is that they are solved promptly, and this is the case!

This is one of my all time favourite addons, so it was with horror and dismay, after it having worked without a hitch since the day I installed it, I awoke one day to a totally blank OneTab page staring back at me with terse and cold indifference. The "OMFG, no, no, no, no, NO, this can't be happening!!" factor was real!!

But! Having regularly taken advantage of the backup option, I was somewhat hopeful I could fix things and lose only a couple of days worth of new tabs. Unfortunately though, no amount of disabling/re-enabling or uninstalling/re-installing could bring back the last tabbed days of my online life. Then, having nothing to lose, I decided to revert to an older version as suggested by a user further down the comment line:

https://addons.mozilla.org/firefox/downloads/file/3359470/onetab-1.29-an+fx.xpi

Oh blessed be!! It's back! It's all back! I could hardly believe it! Whew! Cheers of joy, high fiving myself (and the cat) and a couple of woop woops broke the tense and mournful atmosphere and I was back in business, baby! :) (Shout out to Keegan Witt for the link to the old version. Thank you, my friend! Thank you!)

So... Despite the heart attack-inducing shock of potentially having lost all that was dear to me (tab-wise anyway) I am giving this addon 4 stars. When it works, it works like a dream, so I won't punish the team who made this otherwise brilliant addon by giving a lower score, because do you know what? Sometimes, shit happens. Yup, sometimes it just happens, even to the best of us. The fatal errors in the new version are most certainly not done intentionally and I feel a great deal of compassion and empathy for the poor developer/s who are maybe having a minor heart attack of their own, sleepless nights and they're probably (hopefully) working feverishly in a panicked sweat to fix whatever went wrong and get things back on track. I just can't bring myself to jump on any "cancel culture" bandwagon and diss or abandon this addon after all it has done for me, and besides, I am hopeful there'll be fix soon.

So, to keep this review short, (Yikes! Too late!) I still request a donate button somewhere on the OneTab page and I will be thankful and grateful and happy for having this FREE addon available to me. When it works, it's a little piece of heaven.

So as I said, 4 stars it is, and now I'll be off. I have some more tab-hoarding to do....

Rant over.

Edit (a couple of days later): I'm upgrading my rating to five stars. Turns out all the blame for the temporary malfunctioning of the addon lies with Mozilla and not the OneTab addon. Installed the latest fix and everything's back in perfect working order.

Could be an excellent Add-On, but has problems with keeping data when Mozilla releases new firefox versions. I recommend strongly to frequently save links to a text file. Otherwise you must restore lost tabs from firefox' history.

I've been using OneTab for the last four months and I loved it. I was now working in three projects with around 50, 20, and 15 tabs each. I was able to just group all of the tabs when I was not working in a specific project. I loved that I was able to name each group. But today, when I updated Firefox to the 80.0.1 version, OneTab did not reload my lists of tabs. It was just a blank page. I copied the URL, I restarted firefox, I also restarted windows... It did not help, OneTab was just not working at all. So I removed and installed the extension again. it works now, but it won't reload my previous lists of tabs. I have lost research work done during several months. I can't believe it.

Right now I am just trying to find an alternative.

Great Addon, just lacking a dark mode. Please add it & save me from going blind at night xD

Excellent extension. You can save your open tabs, rename the group share and save. I find it really useful.

Disappeared with all my data!!

Пользуюсь во всех браузерах. Нет резервирования списков - приходится делать это вручную.
В Firefox 80 периодически "пропадает" OneTab - приходится идти в меню "Расширения" выключать и снова включать OneTab. Несмотря на многолетний стаж расширение недоработано, на мой взгляд. С первого момента его создания, сколько бы оно не обновлялось, не вижу никаких улучшений. Жаль, что хорошая идея не реализована в полной мере.

User experience becomes increasingly broken after each update. First it deletes all tabs (the one thing it's supposed to do), and it updates and it won't function unless you manually restart it each time you want to use it (and some people have also lost all their data)

When it's working it works, but that's the only thing I can really say, outside of those times it's an unreliable mess where you spend half your time counting down until the next time it deletes everything

[I am changing my rating from 4 to 5 stars, since the Firefox bug has been fixed.] I "can't live without" OneTab, as it's THE daily tool I use for tab management. LOVE the simplicity & functionality! Way better than bookmarking tons of pages I'm reading/researching but may not want to keep later. BUG NOTE: Reviewers who still have problems with the bug simply need to update their Firefox browser. (Even if you don't, the work-around on old browser is very easy. We didn't LOSE our old links like some have reported, though it was very upsetting when it seemed like we did.)

This add-on is working perfectly once again. After a slight glitch, everything works as it should. One of my fave add-ons, as it reduces tab clutter instantly! Highly recommended.

Edit: Developer fixed the issue and quickly responded to my review. It was an unfortunate bug but I am happy with their fast updates and customer service.

Great add-on but the last update broke it. I need to disable and enable it to get the add-on to work

A very good addon until the last update. Now I have to disable and re-enable it each time I open firefox to get it to work.

Je trouve cette extension vraiment bien MAIS elle se désactive systématiquement à la fermeture du PC!!! bref si ça continue je chercherai une autre application. Décevant

Lost all my tabs in the last release. Tried all the fixes, turned off and on, and did a reinstall. Use the export feature to back-up my tabs, but it doesn't save the headers, or the starred order, so, more work. It seemed okay but today the whole add-on has disappeared? Very poor, have given up on this add-on. I'm using Simple Tab Groups instead, at least it works.