While substantially improved from previous versions, this is still a broken extension. Since sites can only be added by visiting them, you are prevented from adding some sites which use multiple automatic redirections in their login process. Other addons like Containerise or Sideberry handle this without issue. The inclusion of nagging about Mozilla VPN makes this the most commercial of all container addons.

Previous versions were much worse; opening the site list for a container actually allowed all sites on that list to place cookies in the current container, this bug has been fixed and the default containers in containers.json (Personal, Work, Banking, Shopping) no longer have tracking IDs. Before this was fixed, this addon was a net negative for privacy.