[infensus]

It's using tab hiding, one of Firefox's non-standard extensions to the WebExtensions API. I believe this is also how Panorama used to work

By the way, built-in tab grouping is also on the list of features in development. Hopefully they don't go the Chrome way

[godelski]

That's good to know. I've found that it is helpful to add Auto Discard Tabs, if you're a real tab hoarder.

What is "the Chrome way"? What I'd like to see is that the addresses are not cached to ram, but either disk or swap (or a combination). I figure these tools are more used by tab hoarders as well, and if they're working as pseudo bookmarks (at least conceptually) I am very willing to trade some loading time and have non-active tabs have high niceness.