This is a great extension, one that I've been using for years, but the last update has MAJOR problems. It stoppped working on Firefox ESR 115.7.0esr (64-bits), the workaround suggested by its creator didn't do anything. On Firefox 122.0 (64-bits), the extension was apparently ok, but then I used that workaround giving permissions to "Read and modify bookmarks" preemptively and all my bookmarks were gone. DO NOT USE THE WORKAROUND.

With update 3.9.21 it just doesn't work. It doesn't show any tab in the tree when I first lunched Firefox, and left clicking the icon on the toolbar does nothing. Sometimes I managed to open again the extension by disabling and enabling it again, but tabs still won't show. I rolled back to 3.9.20 and it works well again (if memory gives me problems, I'll roll back to 3.9.19). Still, I want to give you 5 stars since I know you will fix this and I love the extension, thank you for it!

Edit: I updated to 3.9.22 and it's fixed, thanks!

Since the last update (3.9.20/jan 2024), extension slowed down everything, transforming FF in a memory eating black hole.

Please debug ASAP.

Rolled back to 3.9.19 and everything seems to be fine!

Раньше было более-менее нормальное расширение, а с последним обновлением это просто невозможно стало использовать. Жрет память как не всебя. За 7-10 минут использования и перехода по 10-15 вкладкам из 150 сожрал 23 ГИГА ОПЕРАТИВКИ, причем все остальное (дополнения и открытые страницы) уложилось в 4 гигабайта оперативки.

J'ai utilisé l'extension durant 3 semaines et depuis 1 semaine, l'extension à des fuites de mémoire
Ayant l'habitude de jouer avec une page web en fond, cela à fait planter mon pc à plusieurs reprises avant de trouver la cause du problème. C'est inutilisable actuellement et je suis passé à une autre extension.

I estimate that TST, all by itself, nearly doubles Firefox's memory footprint. Sidebery freed up 5-10G of memory for me by comparison (yes, way too many tabs...). TST should *not* be a recommended extension. Latest update of TST leaks memory *very badly* and crashes, taking other Firefox extensions and other desktop programs down with it when the OS starts killing things to free up memory. Sidebery is *much* more responsive & performant with a very large number of tabs. This alone will remove a huge amount of friction in reducing the number of open tabs. No more waiting for TST to catch up. Switching to Sidebery was no problem: all nesting retained. Disable TST. Install Sidebery and verify ok. Remove TST. Done.

I have been using TST for about 2 years. It is great and works great for a vertical tab setup.

This is how tabs should work, especially on widescreen monitors.

This add-on makes shopping and doing deep dives so much more convenient. Tabs that go together are automatically shown together.

And for when you don't need it, you can quickly toggle the tab bar on and off with F1

Love this extension as it's made it easier to move about from Edge. I would like to see the side bar auto-collapse, showing only the favicon.

Useful, polished, heavily customizable. Overall an amazing extension.

This add-on made me change my entire browser experience, once and for all.

I was fighting with tabs for so many years. Constantly having a multitude of open tabs, fearing accidentially closing the window.

I was not very productive, having to scroll and look for tabs all the time.

This add-on was recommended to me, and while it did take some getting used to, I was finally able to conquer the vertical tabs.

Now I've move on from Tree Style Tab, to the more powerful Sidebery, but this is what made me do the jump.