SharePoint 2013 adds many great things but for those of us that develop & test solution and need to do so as different users, we’ve noticed the “Sign in as a Different User” option is missing from the Name/Welcome menu. To make matters worse, on some machines/browsers, even if you log out it will not let go of the last logged in user.
Now there are at least a few blogs out there which explain how to modify a SharePoint system file within hive (which, remember, can also be overwritten/undone by a Microsoft update) to add the option back to the menu globally. However, what if you don’t want the option in the menu for all users, all the time; or you don’t have access to the physical server, or don’t wish to modify said file? The good news is that there is a simple trick to force the “Sign in as a Different User” prompt to appear.
All you have to do is add “/_layouts/closeConnection.aspx?loginasanotheruser=true” to the end of your site URL and that’s it. It will log you off and bring up the Sign in prompt so you can login as a different user.