Forgive my ignorance, but I think the thing OP linked is also an addon?

pricci · on Jan 20, 2021

Firefox has the containerization built in. You can use it without the extension but with worst UX.

> For advanced users: You can also enable Containers without the Multi-Account Containers extension, by changing some preferences in the Configuration Editor (about:config page). Note that you will get a better user experience by installing the extension but, if you choose not to, you can set privacy.userContext.enabled to true, privacy.userContext.ui.enabled to true and privacy.userContext.longPressBehavior to 2 in about:config.

https://support.mozilla.org/en-US/kb/containers

marcolussetti · on Jan 20, 2021

You are not wrong. However it's a first-party extension, as in it's from Mozilla.

Debatable how significant that is as a difference.

toyg · on Jan 20, 2021

It’s an addon from Mozilla itself that just surfaces a bit of UI for advanced controls. The actual feature is already baked in the browser, they’ve just been very conservative about exposing it to everyone.