incognito shares state between tabs. temporary containers can have a fresh container for every tab, so your tabs are isolated. you can also use it in a way that by default every site you visit is using a temporary container, with certain urls set to use their corresponding long term containers -- if i go to github, it opens in a github container, if i click a link to some random dev's site, it opens in a temp container, etc.

to provide context, i still use incognito, but i consider incognito mostly about hiding things from myself -- i use it almost exclusively for porn, because i don't want my porn habits in my browser suggestions. temporary tabs still land in the recent urls and such.

You keep your browsing history for one but clear the cookies out after automatically.

Incognito isn't as private as the name suggests. I was surprised one day to open a tab in Incognito and see the site I visited knew who I was. That's because I had logged in to a related site in a tab I'd forgotten about in another Incognito window.

My assumption up to then was that each newly opened Incognito tab or window was it's own private session, but this turned out to be wrong - they all share state, as if you had one separate but shared profile called Incognito. This was a little upsetting as I'd been using Incognito for years without realising the data sharing going on.

Temporary Containers does what I'd expected from Incognito. Each new temporary container has its own isolated cookies etc from all the others. So now I open a TC when I want to visit a site without identity or tracking, or to login temporarily with a different account, and don't use Incognito at all.

For what it’s worth, Safari’s incognito mode works exactly how you described it — separate session for each incognito tab/window.

So you can't open two tabs for the same site and share the session between them?

Correct, not in the private browsing mode.

Some websites are able to detect running in incognito mode because some browser APIs are disabled there, but not in temporary containers

You can restart your browser without losing what's it your incognito windows.

So it stores full state when the application is closed, that's a long way off "incognito". Was it always like that?

I expressed myself poorly. In retrospect it sounds like the exact opposite of what I meant, in fact.

What I meant is if you open what you would otherwise open in an incognito window in a container instead, you can restart your browser without those tabs being closed and the respective state being lost.