Cannot save settings for multiple container of a same site. And when I reload, the duplicates will gone or will only use one container.
Which is not what I expected. Well it does what it does but the way it does it makes me think the title is a bit misleading.
Multi-Account container? NO just call it Firefox Web Container please. Or Firefox Multi-Web Container.

why did you remove this functionality in the newest update to Firefox? why are you making the program worse rather than improving it?

Extremely helpful for web development. Makes it trivial to access the same application with different credentials at the same time.

Amazing. Missing feature to set a start page for Container type

Easy to use - works every time

This add-on alone is a reason to use Firefox

Months later, this remains an incredible tool that is hamstrung by severe bugs.

For example: you can't sync containers between Windows and Linux. You can sync containers created in Firefox running on Linux with other Linux installations, and you can sync containers created in Firefox running on Windows with other Windows installations. But sync across OSes, and you'll wind up with two independent sets of containers synced to the same account.

Another example: the extension frequently spams dozens if not hundreds of additional containers. If my list looks like "Facebook / Google / Shopping", then one day I'll have "Facebook / Facebook / Google / Facebook / Google / Facebook / Facebook / Facebook / Facebook / Facebook / Shopping / Facebook / Google / Google / Google / etc". Because there's no way to clear out your sync data, the only way to fix this is to completely delete and re-create your Firefox sync account or trigger a password reset.

Another example: When you win a badge ("hooray! You just opened 100 tabs!"), it stops using containers. Eventually you'll click on the extension to find out why the heck it stopped working. That's when you find out that alerting you to whatever stupid "award" you've won is more important than actually doing the one job it has.

This has the potential to be a game changer, but it's just a half-baked pile of garbage.