With a few ergonomics this could be the biggest development in web browser in 5+ years. It should really be a build in feature of firefox. It gives you a huge amount of control over your privacy and productivity.

Tracking, sessions, and cookies are completely prevalent on the web in 2018. Every site uses cookies, and every other site has a login. Container tabs give you control over that by allowing you to run a different browser session in each container. You can
- prevent tracking by isolating Facebook, Google, and company in their own containers
- Easily sign into many accounts at once
- Use sites while both signed in and out of them
- organize your tabs with colors
All of this is way more convenient than browser profiles because you keep your bookmarks, history, and settings across each container tab.

There are a few downsides to this addon that keeps it being a full 5 stars.
- Your settings don't sync between browsers
- Setting up the containers is annoying
- Limited options for container tab colors and icons
- when other applications open sites in your browsers it doesn't work very well with the containers
- No central place to see all of the sites you have chosen to open in a container