A few weeks ago I began work on modifying the cookie system on Firefox to support multiple “containers”. Multiple Containers enables users to log in to many websites as multiple users on the same Firefox session. It is very useful for web developers who require this functionality to test their user account systems. Another use is for people who have multiple web mail accounts with the same provider that they want simultaneously logged on to. This is an oft-requested feature that Internet Explorer partially supports. (See bug #117222)
I’m happy to say that this is now ready for testing. Below is a working build for Windows. It is based on the latest Trunk plus the cookie patch and extension. Unfortunately for Mac and Linux users that wish to try the patch, they will have to manually compile Firefox with the patch below.