I'm trying to open the Profile Manager in order to create a 'developers' profile. I was originally following this blog's instructions using the Run command. http://blog.mozilla.org/addons/2009/01/28/how-to-develop-a-firefox-extension/ The problem is that it's just opening up a new Firefox window, and nothing else. I then went to get more updated documentation, here: https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles?esab=a&as=aaq And alas the same results. Here are the commands I have tried: firefox -p firefox -P firefox -profilemanager firefox -ProfileManager "C:\Program Files (x86)\Mozilla Firefox\firefox.exe" -p "C:\Program Files (x86)\Mozilla Firefox\firefox.exe" -P "C:\Program Files (x86)\Mozilla Firefox\firefox.exe" -profilemanager "C:\Program Files (x86)\Mozilla Firefox\firefox.exe" -ProfileManager They all return the same result, which is just opening a new Firefox window.