[6ak74rfy]

How is this different from Tree Tabs?

[Manishearth]

There's no tree, it's flat. I find it works better than Tree Tabs at the moment unless you need the tree.

[idlewan]

Shameless plug: the current lack of a WebExtension for vertical tabs bothered me, so I wrote one: https://addons.mozilla.org/en-US/firefox/addon/vertigo-tabs/