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.

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.

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

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