This blog post discusses integrating multiple external identity providers in ASP.NET Core Identity applications using Duende IdentityServer.The application acts as an identity provider for local and external users, handling claims mapping for each external authentication provider.Using Duende allows for robust OAuth and OpenID Connect authentication flows not supported by some other providers.Each external provider implements a separate scheme for the OpenID Connect flow, with options for shared or unique schemes.The article showcases how to configure external providers like Auth0 and EntraID using OpenID Connect in ASP.NET Core Identity.When using Microsoft.Identity.Web, a separate scheme is necessary for callback and logout handling.Claims mapping from external providers back to UI applications can be managed using Duende's IProfileService.For ASP.NET Core Identity-only solutions, claims transformation can be utilized for mapping claims.References to Duende IdentityServer documentation, Microsoft ASP.NET Core Identity guides, and sample code repositories are provided.