Absolutely great add-on!
Should be a built-in (or added by default) feature.
It's my No#1 tool for keeping services separated from each other, e.g. Facebook separately contained, News websites with their tracking cookies separately contained, other user accounts/profiles in various other websites and/or services w/o any association between them all.
It's like having multiple, persistent "Private Browsing / Anonymous" tabs with the ability to define a persistent default container for every website (e.g. clicking a Facebook link will always open up in a pre-defined Facebook container tab).
I love it and use it all the time!

Very good idea, needs more work, but nevertheless extremely useful in 2019s internet

really needs to be a built in feature, love it!

It is an excellent addon. I like the way each URL can be added to different containers. It is very simple. Maybe the next step is the way to make a backup or sync.

I really appreciate this plugin. Could you please allow us to backup our settings ("always open this site in ..."). Thanks again!

Amazing.

No more having to juggle accounts on Gmail or outlook or SharePoint or etc.
Perfect for those of us that are contractors and work for many different companies.

Love this. BTW, does it sync?

I think this is novel and quite a good one.