Old perhaps, but userfriendly this is not.

I wonder how many users understand the concept of profiles and the session isolation they provide, want to use them, yet find the command line too difficult to use.

Most user won't even be aware of the possibility of using profiles, ask any of your relatives.

While if you had a "Create a new profile" button that does it in one step and that they would advertise on install much more people would be using it, even if it's just for family members separation.

Old Netscape/Firefox builds used to start with the Profile creation/selection screen by default (which is the -ProfileManager CLI option that remains today) and someone can correct me if I am wrong, but the consensus seemed to be that it confused people more than it helped them.

The majority of people already separate family members with different user accounts on the machine or mostly just don't seem to care.

This seems to be the interesting UX compromise that the new "Container Tabs" is trying to meet "where they live": the users that could use some of the advantages of profiles without the full overhead of using multiple profiles. It will be interesting to see if the compromise is picked up by average users.

(Fwiw, I've used multiple profiles in Firefox off and on for decades but have yet to find a relative I'd recommend that to.)

That was then, and this is now.

In the old days, seperate profiles were used to seperate Moms browsing from Dad's browsing. Now, we need different profiles to browse: one for shopping, one for banking, one for work...

Seems to me that coders forget that people evolve. Same with Moxie saying that it is fine for WhatsApp not ticking the 'tell me when the key changed'-box by default because that confuses people. Perhaps it /did/ confuse people, when security was not a known issue. People tend to learn, in my experience. You can't say: "Well, we did an A/B test in 2002 and now we're done for the next millenium."

Uh, right, people could use one for shopping, one for banking, one for work, etc... but they'd like them all to be in the same window so they can switch between them as tabs... (It's funny when you realize that the old ProfileManager predates tabs.)

Which is where we arrive today with Mozilla's work on "container tabs". The code and UX evolve, too.

I'm not sure what your complaint here is, mverwijs? That Mozilla should test Firefox starting up with the ProfileManager again? Like I said, I think "container tabs" might be a good way to do this in a way that mainstream users might pick up and this will be interesting to watch.

(I guess one trick that might be interesting if there was a way to easily "graduate" from I know/love "container tabs" to "oh, the next thing I can try is profiles to do more complicated things", but I think the answer is that profiles will adapt more to work with "container tabs" UX than "container tabs" UX will adapt to the old profiles UX. Given "incognito" tabs in other browsers can be seen as a specialization of a "container tab"/"profile tab", I suspect mixing profile tabs in a single browser window is a UX that is here to stay.)

Since they're akin to user accounts on windows, I'd assume a decent number of users understand them.

Even though people don't use multiple-user-accounts too much anymore, it's still usually present in schools and in older family computers.

Conceptually they're very similar.

there are extensions like switchy that handle the UX part in a reasonable way.