This extension is okay but has at least two major issues:

• It's a massive pain to do things that require third-party sites, for example, if you put Google into its own container, logging into StackExchange sites using OAuth or logging into YouTube become quite the ordeal. 😕 Likewise, you can't log into YouTube unless you reassign Google to "always in" YT's container, then log in, then reassign Google back to "always in" its own container. It's a MASSIVE pain! Similarly, if you put eBay in one container and PayPal in another, you won't be able to make purchases anymore because you can't log into PayPal through eBay. 🤦

• Likewise, there's no way to use wildcards or container-ize subdomains, so you have to add them all manually. For example, you can't put ALL StackExchange sites (*.stackechange.com) in a container together, you have to manually visit each one individually, then do the multiple clicks and mouse-movements to set it to open "always in se container". And then, you have to do it ALL OVER AGAIN for each one's meta subdomain. 🤦 Not only is it a massive pain, but it also defeats the point to containers since SE can track you via all the other sites that aren't in a container, including drive-by one-off SE sites you might find yourself on where you don't even have an account. 🤦🤦🤦

• I temporarily disabled the addon to try to debug an issue with a site, and when I re-enabled it, ALL of its settings were gone, all the containers, all the assignments, everything. Worse, restoring the containers from a backup doesn't help because it already WIPED OUT ALL THE COOKIES! 😠 Apparently this has been a bug for a long time and they STILL haven't fixed it. (I guess they're too busy wasting their time integrating Mozilla VPN. 😒)

• It also doesn't seem to work for this site (addons.mozilla.org), I checked the code to see if they put an exception for it (for some reason 🤨), but it doesn't seem to contain one, it just doesn't work. (Maybe Firefox suspiciously treats this site in a different way at a base level. 🤔)

• The interface is extremely lacking. There is no way to directly edit the settings such as a text-box to enter domains to assign containers. The only way to do so is to actually go to a site and then assign it to a container. This has numerous problems:
◦ It allows a site to track you at least once before you assign it to a container.
◦ It doesn't work if you're offline.
◦ It doesn't work if the site redirects to another domain or even subdomains (eg www.), so it can harvest data and quickly redirect, passing the data and preventing you from assigning the original domain to a container. This addon NEEDS a proper UI.

Missing export/import capacity.

This extension does not work.
Try the following on firefox. Log into an Amazon account in a container in one tab, then open another container tab and log in to another separate Amazon account. Go back to the first tab and refresh the tab. The result is that the first tab now shows the account info of the second tab Amazon account.
So in effect these multi account containers tabs do not isolate anything at all.

No complaints but for the love of God. Can we please have this on android already!

*Edit

Changing my rating to 3 stars because containers constantly break the User-Agent Switcher and Manager addon. I really thought that issue would have been fixed by now.

Also fighting with this app at root domain level is a nightmare. Doesn't know the difference between Google account 1 and Google account 2.

La extensión me encanta pero no funciona bien con sitios donde tienes que entrar con SAML2

Honestly unclear how to use this ext properly. Seems as though Mozilla VPN client (stand-a-lone app) must be turned on in order for containers to fully function as expected (that is the VPN client I'm using). But the VPN app already encrypts all traffic. If this ext is just to segregate tabs for quick access and set specific endpoints then great job Mozilla. I was more interested in having the web traffic routed through VPN without needing to have the VPN client active. Like if you are gaming on one screen while shopping on another, esp. if the game requires Anti-cheat, having the VPN enabled doesn't work. Maybe its just my understanding of what this is intended for...? pssst... new feature Mozilla :). In any case it works great for keeping tabs organized into buckets, as well as setting individual VPN endpoints for each.

There is a very annoying problem: I selected "Remember my decision for this site", and selected "Open with container", then opened a new tab, and then opened the same site, and the prompt appeared again! I've searched the settings and there is no option to remove this site prompt! Also, even though I've opted not to open the container, it still opens as a "private" container, and I can't find an option to remove this site's settings at all.

annoying 4 preset containers, cannot hide and coming back every time i install the addon again, even with sync enabled. Whats more, sync experience was back.