This clashes with your "Firefox Multi-Account Containers" extension, all of a sudden this doesn't work anymore with facebook.com.

Seriously awesome and quite necessary

Great idea, unfortunately UNCLEAR how to add exception

I thought I'd try this, and found that one thing it does is make it impossible to log into a site if you're using facebook to log into that site. When I clicked on the add-on icon I could get a list of sites that were allowed, and there was a section for sites *I* had allowed with nothing in it. And I could find no way to add a site to it. Not by clicking within the app icon. Not by going to manage add-on. And when I googled for help I found a page that said you can add sites but didn't explain how!

Had to remove it.

nice !

Facebook messenger

When I use the facebook container it takes the inbox page out and will not allow me to write post to my business page. The minute I disabled the container I was again able to see my inbox and write post.

It's simply brilliant. You don't realize how much FB and co. snoop on our web activity.