Most recent update asks for a new permission: "store unlimited amount of client-sided data."

No.

https://addons.mozilla.org/firefox/downloads/file/767772/onetab-1.25-fx.xpi

Open the link above directly to cover the installation of version 1.25. Note that it is not to uninstall version 1.26 before installation, but to cover the installation of version 1.25 directly on the basis of 1.26. Lost tag page groups can be retrieved. May the Force be with you!

直接打开上面的链接，覆盖安装1.25版本，注意不是先卸载1.26再安装，是直接在1.26基础上覆盖安装1.25版本。可以找回丢失的标签页群组。祝原力与你同在！

Absolutely outrageous. DO NOT USE IT. Sooner or later it will clean ALL the links you stored there. I wonder why this buggy and poorly coded add-on is still available on Mozilla's website. It's time it was removed from here once and for all!

Always lost my tabs within 3-4 days. Not Worth it.

ONCE AGAIN I'VE LOST ALL MY TABS........!!!!!! THEIR ONLY JOB IS TO KEEP TAB SAVED. DO NOT RELY ON ONETAB. I'VE JUST LOST HOURS OF RESEARCH

ask us to downgrade but didn't provide tutorial for it! i still lost all my tab after it !

well... be ready to lose everything at each update !
EDIT : OK ! reading the comment you can find a fix (downgrading to the previous version restore the tab list ! )
but come on... most people won't even bother coming checking here... either automating the export before each update... or a warning to do so would solve this :/ !

ALL of my tabs were gone. Ridiculous......（EDIT: Try downgrading, but DIDN'T bring back my tabs......）

It f*cked up all saved tabs. Second time. I haven't been making backups too often due to info from forums that previous version is free from this problem. The last version came without any wornings and deleted all tabs.
Unfortunatly the method, that was mentioned in commets.
If you use it, everytime make a backup via html doc.
Now I have to go - I need to get through the entire history for at least a week. F************ck!
F*ck the devs.

Lose all tags with great probability, you don't know when it will happen

Two days ago I would have given this a 5-star rating. However, today ... all my saved tabs are gone! I see it's been two years since this has been updated and, given the number of unanswered complaints, I am guessing this won't be fixed. I am using Ubuntu 18.04 and can't find any help to recover the tabs. Oh well, moving on to another I guess. Too bad. It was great once.

STAY AWAY!!! This shit just deleted about 200 tabs for me by moving only 47 tabs to the OneTab window when using the send all tabs from all windows to OneTab feature, closing all tabs one by one and then closing the windows, so restoring the windows with Firefor built in feature only brings back ONE tab per window and not even all windows (3/10). As you can imagine i'm quite upset by this.

It loses your tabs! Beware of this possiblity. It was last updated 2 years ago so may be incompatible with the latest firefox.

Used to be good. Now on occasion when click 'bring all tabs into onetab', all tabs are closed but are not brought into onetab - ie they are gone, gone, gone. An extension of this type has to be consistently reliable, else it's worse than useless. They don't seem to be updating it, so I guess it's dead.

Almost useless. Does not save "new tabs" and pages like "about:config". Reverses the order of tabs and does not allow to save tabs in file on disk.

WARNING: This extension does NOT save your windows with tabs. I was hoping to find an addon for firefox similar to Cluster Tab Manager on Chrome, so I thought this would be it.

NOPE. This only temporarily condenses your tabs and they will NOT BE SAVED for later. You could " star" a tab, fooling you into thinking it will be saved for later (like when you want to open up a new window and load them up there) but it WILL NOT. Not only that, but the buttons on the UI are very unintuitive. SO MANY BUTTONS just mass condense your tabs without asking which tabs you want to be saved. Some of these buttons will also even automatically delete the condensed tabs after a couple seconds without user input!

So many good porn tabs lost in an instant... Might as well just go back to using my already cluttered and filled bookmarks manager...

Not functional on Android even though there is no notice of incompatibility.

EDIT: do NOT update - it will delete your save tabs

does NOT save data/ tabs when firefox restarts. I've lost all my onetabs TWICE

not works firefox 56

I recently installed it (I know the extension because of Chrome) and it's not working at all on Firefox. And I lost the pages I had.

Tengo en cada tab una página a una emisora de radio, al usar OneTab se dejan de escuchar cada una de las emisoras en cada tab. No me sirve así

"Bring All Tabs into OneTab" loses all your tabs from other windows and the developers have known the loss that occurs for many many months, if not years. Used to be My Favorite extension.