The announcement begins by referring to different versions (nightly, beta, stable, etc.) of Firefox as "installations", and then switches to "versions" halfway through. I was momentarily confused because it seems to suggest that every time Firefox updates itself, e.g. from 67 to 68, it will use a different profile.

Which it most likely won't, but one cannot be entirely sure about that assumption in a world where software updates frequently reset user settings to vendor-preferred defaults without asking.

The fact that nightly, beta, and stable really are different "versions" of Firefox (current beta becomes the next stable) makes the terminology even more confusing :(

Is this the worst-written announcement ever, or am I going to lose my settings when FF goes to version 68?

I think by versions and installations they intended to refer to release channels.

I thought this was the default? I've been running firefox and firefox developer for a while now and they have never interfered with each other, maintaining separate things such as remembered passwords and histories.

Previously, some editions had different profile folders while others shared the same.

i.e. Firefox Developer had its own profile, but Nightly and Firefox shared the same, which was a PITA for the latter case.

Now all editions (thankfully) will have their own respective folders.

This seems like a way to force users into using Sync. I refuse to use that for privacy reasons. Do not want.

You can run your own Sync server if you want [0]

[0] https://mozilla-services.readthedocs.io/en/latest/howtos/run...

I had ESR and regular Firefox installed so that I could use Google Hangouts last year after they dropped plugin support. After a particular upgrade (don't remember which), all of my data just disappeared because the profile formats were different and Firefox decided that the file was corrupted.

Thankfully I figured out what was going on, and they saved a backup of the "corrupted" file that I could just put back into place.

It seems like absolutely the correct solution to have each release to have its own profile.

Why would you assume they're trying to force you to use Sync? This change is being done at the request of a small subset of people involved in testing and development.

Is there a real world usecase where someone needs to have two versions of Firefox installed and it's beneficial to have shared profiles?

I would think someone paranoid about security and privacy would want different profiles so all your eggs wouldn't be in one basket.

Doesn't sync encrypt the data sent out with keys only known by you? So in that case the main loss in privacy seems to be that others learn that someone from your IP uses Firefox sync. Are there other privacy-oriented reasons to avoid it?

edit: Now that I think about it, it does also seem to force you to use a functioning email address as opposed to say an arbitrary username. That is something I never liked.

Firefox profiles are already not guaranteed to be compatible between versions. Sometimes this causes problems when sharing a profile between a Release version and an ESR version. For example, FF 55.0 moved favicons to their own file, favicons.sqlite, and FF 52 ESR would not be able to read favicons from the profile any more.

You can achieve the same effect by reusing the profile, though I've heard it can be buggy due to forwards/backwards compatibility issues esp. in add-ons. It requires a bit of technical effort (launching firefox with the -P flag to open the profile manager, or editing profiles.ini directly), but if you're using several versions of Firefox chances are this is not a problem.

OMG it's finally happening! I've been waiting for this for sooo long. I'm excited! :D

Does this mean if you want to keep your profile when upgrading Firefox to a new version you will have to have a Firefox Account to sync your settings? I do not think that Sync carries over extension settings (e.g. all the custom site settings for µBlock).

Most likely not, but I understand that the terminology is confusing. (See my other comment in this thread.)

Will this allow you to run several profiles side by side using the same version of the browser, like with Chrome?

Other people have already answered your actual question, so I'll weigh in on my assumptions of your use case instead :).

I find that multi-account containers give me much of what I would otherwise gain from running in multiple profiles, in as much as cache, cookies and other state are separate, so I can be logged in to a different set of accounts in each container. Temporary Containers makes life ever easier -- a whole new empty state at the push of a button, and parallel non-shared state: it's much more usable than Incognito for web development and testing.

On the other hand, if you want a different set of extensions then multi-profile is the only way to go.

https://addons.mozilla.org/en-GB/firefox/addon/multi-account... https://addons.mozilla.org/en-GB/firefox/addon/temporary-con...

I think you can already do that?

Yeah, just start the profile manager (firefox --ProfileManager), create a new profile, and then run the "other instance" with --profile NAME. Sometimes --no-remote is also helpful, so clicking on some links will not open them in this other profile.

This can also be done from within the browser: navigate to about:profiles.

You can, if you run Firefox with -P and profile name. I run two instances most days.