Have you noticed that in Sharepoint 2013 there is no possibility to log in as a different user ?
The link has been removed or forgotten in the UI.
It has always been a nice feature to have for admins and developers to be able to log in as a different user…
If you miss it so much though the link is still available:
/_layouts/closeConnection.aspx?loginasanotheruser=true
and it still works in Sharepoint 2013.
I guess this would be one of the features that people will ask to build.
Another workaround is to use “run as” when launching the browser which by all means is a safer way…
Happy Sharepointing !!
The Blobfarm 
But it seems that it doesn’t work when forms auth. is enabled ? I got exception…encoded Value..etc.
Hi Kamil,
Sign in as a different user is fundamentally broken, which is why it was removed.
http://blogs.technet.com/b/stefan_gossner/archive/2012/01/19/be-careful-when-using-the-quot-sign-in-as-different-user-quot-feature-in-sharepoint.aspx explains why.
But it seems that it doesn’t work when forms auth. is enabled ? I got exception…encoded Value..etc.
Hi Kamil,
Sign in as a different user is fundamentally broken, which is why it was removed.
http://blogs.technet.com/b/stefan_gossner/archive/2012/01/19/be-careful-when-using-the-quot-sign-in-as-different-user-quot-feature-in-sharepoint.aspx explains why.