Very useful and very customizable.

Log on to the same site with different accounts effortlessly.

I have multiple Microsoft 365 accounts and now they can run in adjacent tabs without interfering with each other.

Great Addon.

I love this extension. "Open this site in your assigned container" create s some problems, but as the Developer response below explains, there is a solution.
"Remember my decision for this site" is useless in some cases. For example, I want to open multiple AWS accounts in different containers. The pages of different accounts have the same url, so "Remember my decision for this site" does not do any good.
However, the second tip - delete the sites assignments to containers works. It just opens a new page in the same container as the original page I'm coming from.
Thank you for the advise and standing behind your extension.

Works great for me and you can sync your settings with your FireFox account

If you value your privacy and want to mess with how we are tracked online, this add on is great.
If you have several users (who trust each other, I suppose) sharing the same browser instance, then this can save you a lot of logging in and out (yes, I know, not a secure practice, hence trust is implicit, but secure or not, it happens).
Both of the above I do routinely, and I have really appreciated this add on for that.
For me, though, where it really shines, is in the following too situation:
- I play a web game where it allows me to be logged in to several instance,
- opening a new container is often a fast hack that allows you to bypass the article count in some websites.

So, in sum, if there is any situation where you would like one browser instance to behave as several instances with separate contexts, this is for you.

And huge thank you for the developers, for coding this, and for doing so in a Free/Open Source app! May your kindness and dedication come back to you and bring you joy!

Amazing. So handy to ensure gmail doesn't automatically spread it's tracking session across all of my browser tabs!

Container history should be separated too even though it seems impossible. Maybe just autofill container separation.