it Containers were already a "killer feature" of Firefox, this is like a weapon of mass destruction feature.

This extension means you can save a bookmark which opens gmail (or drive or calendar) in different containers for different accounts. Because the URL is the same for different gmail accounts, the standard feature of associating a URL with a dedicated container doesn't work: it's the same url for each gmail account, so they always open in the same container. This add-on solves the problem.

This is very convenient.

The notes are not very clear on how to do this.
Do it like so, taking gmail as the example.

Let's say you already have a Work and a Personal container.

First, use the Firefox container tool to remove any rules you have added which force gmail to open in a particular container. Such sites appear in a menu linked to the container name.


Add two bookmarks. You could go to gmail, and bookmark it, if you don't already have gmail bookmark

The normal URL is
https://mail.google.com/mail/u/0/#inbox

edit the bookmark to be

ext+container:name=Work&url=https://mail.google.com/mail/u/0/#inbox

then copy this bookmark to make a second one, and edit the bookmark to be
ext+container:name=Personal&url=https://mail.google.com/mail/u/0/#inbox