Upon clicking a tab group it opened a new window and closed the old, deleting all open tabs without a warning or a chance to restore them.

Then suddenly the created group was empty too.

Really unprofessional and annoying. Just stick to established UI-norms, what's so hard?
Drive4ik can't be voted down enough.

Became spyware. Asked to track extension usage after the recent update.

Works only for less number of tabs. If the numbers increases, it fails and all you work gets damaged. Using for around 1 year now, it crashed multiple times, but I continued using it, since I did not find anything as useful as it was. But now, I don't think it deserves my time. Productive people should avoid using it as one cannot have any idea when it is going to crash, mix few tabs from two different groups, delete few tabs, delete few groups, ruin all your work, add same tabs in a single group for multiple times and the list goes on.

Nothing simple about this extension, it sounds like feature other browsers has, but really it takes just as long to navigate through shitty design that this extension has as if to sort through that 100 tabs you expected to organize.

non-working for my FF, lost of time

If you are an avid collector of tabs DO NOT INSTALL THIS EXTENSION!

As soon as I created my first tab group it instantly an irreversibly deleted all my 100+ tabs -- no option to recover them. This extension was a serious disruption to my workflow and it will take a long time to recover from this incident.

Was hoping for something similar to Chrome's tab groups. App was clunky, difficult to navigate, and slow to use.

It had an error and I lost all the groups I had created. Waste of time, not reliable at all.

Terrible add-on. Used it for just 2 days. On 3rd day, all my saved tabs were gone. Missing. Poof. No explanation. Not simple at all. More like complicated. Avoid at all cost.

After year of ordinary usage just wiped all my tabs and backups too!

Worst. Extension. Ever. Arbitrarily deletes tabs with no warning and no option for recovery.

100% CPU usage

It's good extension but when it has big bug: sometimes tabs in one of the group are duplicated during browser restart.
Update: very stupid and annoying bug, I did reopened the browser 6-7 times and now I have 100 tabs in my Work group. It's so buggy. Can't use it anymore.

Was very exited to use this extension, but sadly it has been extremely buggy. Tab groups break as soon as the browser is closed and opened. The whole plugin breaks and I had to manually disable and reenable the plugin to get it working, only for it to break when restarting the browser.

I LOST ALL OF MY TABS SAVED ON STG GROUPS!!! AFTER SHOW THIS MSG... :((

''
Database error in Simple Tab Groups
Unfortunately, an error occurred while reading data from the STG addon from the Firefox database. At the moment, the addon is stopped. To resume the add-on, do the following:
Restart Firefox Browser (for Linux and Mac OS with process termination)
If you see this window again, try reinstalling the addon:

Remove STG Addon
Restart Firefox Browser
Install STG Addon
Restore the latest STG addon data backup located in the Firefox downloads folder "STG-backups".
You can restore backup in addon settings
''

It is really not convenient. I cannot use multiple groups at once, I cannot use pages that are not grouped. Group switching is very slow, 3 clicks are needed compared to Chrome's 1 click show/hide feature. The menu system is VERY un-intuitive.

This extensions seems nice at first glance, but after using this extension for a while, I view it as being broken. When you open Firefox and you have a lot of tabs already open, you sometime get tab duplication. A lot of the tabs gets duplicated. It makes Firefox very slow to startup. It is unusable in Linux. When you open Firefox, the tabs load without any end. It loads forever and Firefox is unresponsive. So to summarize:

1) Tabs duplication bug
2) Very slow Firefox startup
3) Unusable in Linux, it simply does not work in Linux

I can't rate this extension more than 1.

Cumbersome to use. Not intuitive. I thought maybe I could take a few open tabs out of several and group them. Sure, but now the rest of the tabs are gone unless I also group them. Essentially if you want to group, you have to group everything into groups or you're accessing your non-grouped tabs through a little dropdown. If that's not the case, it wasn't intuitive enough to figure out otherwise or would be efficient to use.