I have been using this Add On for a long time but never had any issues.
Recently, It has started to create an issue.
It says, '' UNEXPECTED ERROR OCCURED''.

I don't know what to do now.

This is so useful for web developers, makes me glad I'm using Firefox. Unlike Chrome's private browsing, every time you click that icon, the new tab has a brand new "cookie jar" so you can be logged into any app with multiple accounts on multiple tabs making debugging a breeze. Also for normal multi-account use.

Ok

WARNING: This addon is no longer maintained! The developer passed away and there is no fork currently.

Awesome use of Firefox`s containers. If you want to use two logins on one site or dont trust a site, this feature makes Firefox`s container isolation very easy to use!

This fixes the official Multi-Account container extension's main weakness.

You can use this extension's "Isolation" setting so than when you click on a result in a search engine, for example, it automatically loads the new site in a temporary container instead of loading in the search engine's container.

Now Google can't follow you to the sites you open through its search results.

Edit: It seems the creator passed away in 2023. RIP, and thank you for the great extension.

this add on has changed my life, love it. it needs way more hype!!!

Seems to leave behind site data for every temp tab and site visited. Maybe Strict mode incompatibility? Whatever the case I've got dozens of listings reporting 0 Cookies but site data is still being stored.