An another significant feature dropped in SharePoint 2013. Sign in as different user no more available by default. this is one of the most frequently used feature in early SharePoint versions for Demonstration and testing purposes. as per Experts around “It has been removed from OOTB feature based on security considerations, specially on production environments“
however still it’s as simple as editing and adding few lines on Welcome page. here I’m stepping you to get it back but I would say it shouldn’t be done in PROD environments as Microsoft has dropped it reasonably.
1. Direct to – C:\Program Files\Common Files\microsoft shared\Web Server Extensions\15\TEMPLATE\CONTROLTEMPLATES\
2. Keep Welcome.ascx file originally copied somewhere and edit the original one through notepad and save it.
3. Add the following element before the existing element with the id of “ID_RequestAccess”:
<SharePoint:MenuItemTemplate runat="server" ID="ID_LoginAsDifferentUser"
so it’ll look like this once you edited
go open up your sites and see. yeah it’s back in there.. Enjoy !