SharePoint 2007 (MOSS) & SharePoint 2010 have an option of “Sign in as different user” in the menu at the right top corner of the page. Developers used this handy menu to test their customizations for different users by logging in with another account. But in SharePoint 2013, you will not be finding that option. You just can sign-out from the site, re-open the browser & login again.
Not sure is it removed with a reason. But MS references say it is a problem with SharePoint 2013.
So, How do I login as different user to my SharePoint site? There are two ways you can do it:
1) IE’s “Run as different user” option
This is the way old method we used to start any application with a different credentials. That is by using the Run as different user option that will be visible if you hold the Shift key when you right-click a program icon.
Start Internet Explorer by using the Run as different user option, where you can provide the different credentials and then go to the SharePoint site.
2) Navigating to the close connection page
More simple way is to browse the close connection page. Hit the below URL in your browser where you have opened your site.
You will be getting a pop up to enter the new credentials where you can sign in as different user.
Note : This option uses an unsupported browser feature which is unreliable and may causes other issues. Currently this option does not work in IE 10 and Safari.
Hope it helps.