SharePoint 2013 doesn't offer the handy "Sign-in as different user" feature as in its previous versions under welcome menu. Not very clear why Microsoft has removed this option, I guess might be due to security/caching problems!
Option 1: Navigate to Close Connection Page
Navigate to the URL: http://Your-Site/_layouts/closeConnection.aspx?loginasanotheruser=true
BTW, The above URL is just copied from SharePoint 2010's Sign-in as different user option, and it works for SharePoint 2013 as well! Replace "Your-Site" with the SharePoint 2013 site collection URL of your environment.Once you hit this URL, you will be prompted to enter your user name and password.
You can also bookmark it! just drag and drop this to Favorites bar: Sign in as Different User
Option 2: Run IE as different user / Open IE in private mode
- Go to Start >> Internet Explorer >> Shift+ right click >> Choose "Run as Different User"
- Or, Go to Internet Explorer >> Tools >> Click on InPrivate Browsing
Option 3: Edit "Welcome.ascx" file
Edit "Welcome.ascx" file, which is at "C:\Program Files\Common Files\Microsoft Shared\Web Server Extension\15\TEMPLATE\CONTROLTEMPLATES" folder. (modifying files in the SharePoint file system is not a best practice, BTW!)
Open it in notepad, Add this new entry under the node: <SharePoint:FeatureMenuTemplate>
<SharePoint:MenuItemTemplate runat="server" ID="ID_LoginAsDifferentUser" Text="<%$Resources:wss,personalactions_loginasdifferentuser%>" Description="<%$Resources:wss,personalactions_loginasdifferentuserdescription%>" MenuGroupId="100" Sequence="100" UseShortId="true" />So the file should look like this:
Microsoft KB addressing this issue: http://support.microsoft.com/kb/2752600
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