There are times it is desirable to be able to login to a web site or web app multiple times with the same or different user accounts using the same browser. The problem is once a user is logged in from a browser there is no way to login again using the same browser since all browser tabs and windows share the same session cookies. And since they share the same cookies the first login will be active for all browser tabs and windows.

Firefox provides functionality called profiles that provides a way to have multiple sets of cookies, history, bookmarks, settings and plugins. This allows multiple browser instances to have completely independent cookies and settings.

<WRAP round info> A browser instance is not the same as a separate browser tab or window. A browser instance is a completely separate and independent execution of the browser. </WRAP>

This allows a user to be concurrently logged into a web application multiple times with the same or a different user account.

The general idea is to use multiple profiles to provide multiple independent sets of cookies and settings. To create profiles Firefox can be launched with an option that opens a profile manager.

Once the profiles are created Firefox can be launched with an option that starts the browser with a specific profile.

To create profiles start Firefox with the Profile Manager option.

To open the Profile Manager run Firefox with the options -P -no-remote. Copying an existing Firefox shortcut and modifying the command line is an easy way to do this.

• -no-remote: allows multiple instances of the Firefox executable at once.
• -P: short version of -ProfileManager option

"C:\Program Files\Mozilla Firefox\firefox.exe" -P -no-remote

• Click the Create Profile button to create a profile.
• Either use the default profile folder or create a folder for the profile data and then select that folder.

In addition to the folders that contain the profile data there is a configuration file that contains a list of all profiles. That file is locate at the following path.

%USERPROFILE%\AppData\Roaming\Mozilla\Firefox\profiles.ini

As an alternative to using the Profile Manager the profiles.ini can be edited directly with a text editor to create multiple profiles. Simply copy an existing profile in the file and use it for other profiles, modifying the profile location to some other folder.

<WRAP round info> When using this alternative be sure to specify a unique directory for each profile. </WRAP> <WRAP round info> An existing profile directory can be copied for use with another profile. By doing so all the settings and plugins from the source profile will also be in the new profile. This may be a desirable result. </WRAP>

Start Firefox with a profile by specifying the profile name after the -P option.

The following command line example starts Firefox with a profile named Weasel. Again, a easy way to create a shortcut to this profile is to copy the general, existing, Firefox shortcut and modify the command line property of the shortcut to specify the profile.

"C:\Program Files (x86)\Mozilla Firefox\firefox.exe" -P "Weasel" -no-remote

URI for accessing raw configuration.

about:config

URI that displays cache location, which indirectly reveals a clue about the current user profile.

about:cache

<WRAP round info> These instructions are specific to Windows, but the same general idea applies to other platforms. </WRAP>