With <authentication mode="Windows"/> in your application and Anonymous access enabled in IIS, you will see the following results:

System.Environment.UserName: Computer Name

Page.User.Identity.Name: Blank

System.Security.Principal.WindowsIdentity.GetCurrent().Name: Computer Name

With <authentication mode="Windows"/> in your application, and ‘Anonymous access’ disabled and only ‘Integrated Windows Authentication’ in IIS, you will see the following results:

System.Environment.UserName: ASPNET (user account used to run ASP.NET service)

Page.User.Identity.Name: Domain\ Windows Account Name

System.Security.Principal.WindowsIdentity.GetCurrent().Name: Computer Name\ASPNET

With <authentication mode="Windows"/> and <identity impersonate ="true"/> in your application, and ‘Anonymous access’ disabled and only ‘Integrated Windows Authentication’ in IIS, you will see the following results:

System.Environment.UserName: Windows Account Name

Page.User.Identity.Name: Domain\ Windows Account Name

System.Security.Principal.WindowsIdentity.GetCurrent().Name: Domain\ Windows Account Name

With <authentication mode="Forms"/>:

Request.ServerVariables["LOGON_USER"]: Domain\ Windows Account Name