It's usable I guess.
The main issues it has are:
1. when forcing a site to always load in a specific container, subdomains are never included. There should be a way to include them.
2. After setting a site to always open in a container, there's an extra dialogue that appears the next time you open that site, which can sometimes render the browser inoperable.
3. It requires a keybinding even if you don't want it to be set to anything.
4. You can't make it so certain sites load in the default container.

Would give it five stars if there were an android version.

Everything seem to work fine. Perfect for separating your google Drive, Docs, Gmail, Calendar and other services from the Google search engine. I have not encountered any major bugs but you should double check that the container that is set is opening the first time you're using it.

I'm also using this plugin in conjunction with the Facebook container plugin to keep Facebook from snooping on everything I do.

if you're using this plugin don't forget to log out from google before adding it to a container so your regular tabs isn't logged in.

I gave you five start

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-----> CAN BE IMPROVE IT :(
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BUG ---> Why always for a new version of firefox I have to set up the plugin even when I have firefox sync activate.

1. Missing --> Not working for Firefox Focus or Firefox Android you have 366,285 Users for sure many of them use android, and there are no plugin you will be the first . Hit first hit twice ;)
why don t port to firefox focus or firefox android or even better integreated with firefox by default

2. Missing --> Better configuration I recomend containers helper https://addons.mozilla.org/en-US/firefox/addon/containers-helper/

3. Missing --> in every firefox version the multiaccount containers icon it desapear from the menu bar

4. Missing --> containers in sidebars https://addons.mozilla.org/en-US/firefox/addon/container-tabs-sidebar/

5. Missing --> Not working in private mode, containers is great to open the same web ex gmail in two cointeiners in the same browser
so I can read work and house gmail but in priveate multi account container doesn t work

6. Missing ---> Automatically open websites in a dedicated container. Simply add rules to map domain or subdomain to your container.
https://addons.mozilla.org/en-US/firefox/addon/containerise/

7. Missing ---> Temporary container option https://addons.mozilla.org/en-US/firefox/addon/temporary-containers/
8. Missing ---> Option of container proxy https://addons.mozilla.org/en-US/firefox/addon/container-proxy

If you disable this add-on then your customizations to existing containers will be lost and any new container you added later will be deleted.

UPDATE: Firefox just (13/2/20) added the sync functionality in this add-on which let's users sync customizations. Will give 5 stars if they also add the functionality of limiting a container only to assigned site(s).
UPDATE 2: They added the functionality. Giving 5 stars now.

Excelente, al principio hay que ir seleccionando que pagina va con cual contenedor, pero despues de hacerlo es super simple ya que se abre automaticamente en el contenedor.

This is THE best feature of Firefox IMHO

won't sync containers between computers. I set-up my containers on one device, but have to do it again on each computer I use.

It's easy to use to help organize tabs! The ability to have tabs/websites auto open into their respective containers is great!

Lovely, simple, and effective :D