Very nicely done. It allows to compartmentalize my online life: one tab for Google products, one for Facebook, one for Amazon, one for banking, and the default for the rest.
Idea for a feature: have a per-container type option specifying whether new links opened from that container should open in the same container type or the default container (or even, specify in which container to open links).

It's a must have add-on. But it causes some serious problems with the copy-paste function throughout the system. As soon as I install this add-on and start using it my copy-paste function starts malfunctioning. I have to press Ctrl+C like 5 times to make sure that it would have worked at least once. It's very annoying to copy something and when you go to other place and press Ctrl+V, it turns out nothing was copied.
Now a days, it has starting causing problem with Whatsapp web as well. When I copy an image from clipboard directly into Whatsapp web, it shows a black image. But if I do the same using google chrome browser, where I don't have this add-on installed, it works fine. After months of headache, I have finally reached the conclusion that this add-on is the culprit.

very helpful tool when managing multiple accounts in one browser

Doesn't work in browsing private mode. Firefox 72.0.1 (64 bit)
Please solve !

This is the single most used add-on I have. My job requires logging into multiple sites with different accounts, and Containers makes it such a breeze. Brilliant add-on!

This is an absolutely brilliant extension, the setup is super simple, you can create as many custom containers as you like. Personally I've kept all facebook owned sites in the facebook container, I've then got one for all google owned sites, one for twitter and then general ones for the different types of sites I visit, so tech, news, general, personal, banking. Basically you create the containers, create a new tab in the container, go to a site and then tell the extension to always open that site in that container. Bingo, you're done. And, the longer you have it, the more sites you find yourself adding to each container. This coupled with Privacy Badger and HTTPS everywhere and I know less of my information is leaking out. I will say, it's sad that the online world has now got to a point with tracking that we have to do this sort of shit. But, if it forces the likes of Google, Facebook et. al. to change their ways then I'm happy to do it.

This is really well implemented -- bravo, Firefox! I'm betting you're using standard MVP approach for releasing this. You've got two more features to add for this to make me leave Chrome behind for good: 1) bookmarks per container; 2) syncing between Firefoxes on different computers.

I know you'll get there and am looking forward to it!

Please please please add support for syncing containers across devices. Containers are amazing and perfect on a single device. But as soon as you have multiple devices it becomes a pain to set them up and manage them on every device. I think ideally there's be an option per container for whether to sync it or not.

I really enjoy the ability to isolate sites with containers. Works great if you want to be logged into multiple accounts on the same website. Two or more gmail accounts open at the same time.

This functionality is wonderful when doing web development. Testers/developers can be logged into all the website roles at the same time if desired. Great when used in combination with https://addons.mozilla.org/en-US/firefox/addon/temporary-containers/

Best solution I found for managing multiple AWS accounts simultaneously.