The Firefox profile manager is a built-in tool that can be used to create, edit and delete Firefox profiles. Each Firefox profile is independent from each other which means that it can have its own set of settings, bookmarks, extensions, plugins, interface and themes. It is for instance common to create multiple profiles for different usage scenarios, say web development and normal surfing or search engine optimization and secure browsing.
Firefox users can start the profile manager with the parameter -profilemanager. Additional information and instructions are available in the guide Working with several Firefox profiles.
Mozilla unfortunately has plans to remove the Firefox profile manager user interface from the browser. What does it mean? It means that it will no longer be possible to launch the profile manager with parameters. The functionality itself will be retained but third party tools are needed for it.
ProfileManager is a tool that has been created by some Mozilla developers to fill the gap.
The free tool is available for Windows, Linux and Macintosh. It displays the available profiles on startup with options to edit, copy, create, backup and delete profiles easily.
The profile manager can handle multiple Firefox versions on the system with an option to assign profiles to different versions of the browser. Launch options are however only available if the browser is started from within the Profile Manager application.
The two new options in the application compared to the current profile manager in Firefox are to copy and backup profiles. Copy basically creates a 1:1 copy of a profile under a different name, backup offers to create a backup of a profile with the option to restore that backup at a later point in time.
Firefox users who are currently working with multiple profiles should keep the change in mind to avoid confusion once the developers remove the feature from the browser.
Profile Manager for Windows requires the Microsoft Visual C++ 2010 Redistributable Package. Downloads are available exclusive at the Mozilla ftp server: ftp://ftp.mozilla.org/pub/utilities/profilemanager/. (via)
Update: Mozilla moved the public repository to a new location. You can download the Profile Manager from the new website located here: https://archive.mozilla.org/pub/utilities/profilemanager/