Internet Explorer 8 (aka IE8) has implemented a change in feature where multiple open browser windows or frames share the same session cookies across all open tabs and windows, including new IE frame window opened via double clicking blue E shortcut or icon and New Window command in menu bar (equals to Ctrl-N keyboard shortcut). The change effectively means that all login and sign on or logout and sign off will be automatically be reflected and affected on all other different IE8’s windows.

The behavior is a departure from IE7 (Internet Explorer 7) where different windows or frames of IE can be used to log in or sign on to multiple different login from the same website or service provider. For example, login to multiple accounts or different login IDs on Hotmail, Google, Yahoo!, Facebook, MySpace, Twitter, Blogger and etc. It’s great inconvenient for users who accustomed to have more than one user account for the same service, and have to login to more than one account at the same time simultaneously and concurrently.

In addition, shared session may open to a security vulnerability where user can open a new browser window and access sensitive private information in a session that available on the other browser window frame. The new shared session cookies between windows also may break some third party Intranet application that expects separate sessions across separate browser sessions.

The change was introduced from IE8 Beta 2 to merge frame process, with just one frame process for all windows that contain tabs on the launch of IE. All subsequent launches will only start a new tab process or make a new tab in an existing tab process.

As a workaround, Microsoft provides a -nomerge switch parameter for IE8 executable. With -nomerge switch, which also triggerable via “New Session” in menu bar, IE8 default behavior will be overridden to start each new browser window in a new, unique and separate frame process, and session. The “nomerge” trick can also be used as an workaround to login to multiple user accounts on the same web services,

Essentially, the -nomerge option switch allows you and me to access different accounts of the same web service (e.g. Google Account) with different IE8 window, such as trick to login to multiple Gmail account. The hack doesn’t stop at Google Account or Gmail, and it applies to virtually all web services available which uses web browser to access.

Tip: -nomerge switch only works on new IE8 browser window/frame, and not new tab.

So, in order to have multiple concurrent logins to a web application, just load a new instance of the IE8 web browser by using one of the following two methods.

Method 1: New Session

In an existing IE8 web browser window, press Alt to reveal and show the menu bar. Go to File drop down menu, and then select New Session.

Internet Explorer 8 New Session

Method 2: -nomerge Switch for iexplore.exe

To start a separate session IE8 browser frame, type the following at Start Search, Run command box or in Command Prompt:

iexplore.exe -nomerge

Run Unique Session Window in IE8

Tip: You may have to change directory (cd) to %ProgramFiles%\Internet Explorer\ folder if the path is not defined in command prompt and/or Run command box.

Method 3: Modify IE8 Shortcut to Permanently Launch New IE Browser Window in New Session

Right click on the IE8 shortcut (all IE8 shortcuts or icons on desktop, Start Menu, Quick Launch bar or Taskbar that you want it to run as a new instance session have to be changed), and choose Properties from the right click context menu. Then, append -nomerge to the end of the of the program path in “Target” text box at “Shortcut” tab. For example,

“C:\Program Files\Internet Explorer\iexplore.exe” -nomerge

IE8 NoMerge To Run Separate Session Browser Frame

For IE8 shortcut that automatically open an URL link location directly, the “-nomerge” parameter should come before the URL. For example,

“C:\Program Files\Internet Explorer\iexplore.exe” -nomerge

Update: Ways to login to multiple accounts of same website simultaneously on single browser session.