This post is a direct response to a comment from the user Digitarius on the post where I detailed my Firefox Security Profile. He assumed that it is not possible to run multiple Firefox profiles at the same time and I would like to use this article to explain how it is possible to run multiple Firefox profiles simultaneously. The prerequisite is of course that at least two user profiles have been created. User profiles are created in the Firefox profile manager which can be started using the parameter -profilemanager.
Firefox needs to be closed to be able to start the Firefox profile manager. I usually fire up the run box using Windows R and type firefox -profilemanager. If you have troubles let me know and I explain it in details.
Firefox can be started as usual which loads the first profile. The command firefox -p profile -no-remote can be used to start Firefox that is using another profile where "profile" is the name of that profile. If you wanted to start the profile securep you would use the command firefox -p securep -no-remote
I would probably create a shortcut to Firefox on the desktop using the parameters if I would be using it more often. To start the profilemanger and select a profile from that gui remove the profile name from the command, e.g. firefox -p -no-remote
Update: Mozilla announced plans to retire the built-in profile manager to replace it with an external program. When that day comes, profiles can only be created with the new profile manager.
This new program does however come with several new options that make it interesting. You can for instance assign specific Firefox versions to specific profiles and configure the browser versions to use the -no-remote start parameter so that multiple versions of the browser can be run next to each other.