ASP.NET HttpContext User.Identity.Name

Platforms Supported: All

Similar to AUTH_USER / REMOTE_USER / LOGON_USER in Server Variables.

${aspnet-user-identity}

Adding Identity in ASP.NET Core 2.2 using IServiceCollection in ConfigureServices:

services.AddIdentity<IdentityUser, IdentityRole>()
    .AddRoles<IdentityRole>()
    .AddDefaultTokenProviders()
    .AddDefaultUI();

See also Introduction to Identity on ASP.NET Core (Configuring IdentityOptions)

For additional details about the user identity, then one can also use ${aspnet-user-claim}