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The Best Identity Providers for .NET

Robert Phillips
Two blue circles

The best identity provider for a .NET team depends on one question: who should operate your token server? If you want it to be part of your own .NET codebase and deployment, Duende IdentityServer is the strongest choice, with OpenIddict as the open-source alternative for teams that prefer to assemble the plumbing themselves. If you want a standalone server product, Keycloak (open source), FusionAuth (free to self-host), and Curity (commercial) lead on the JVM. If you want identity fully managed for you, Auth0 is the strongest general-purpose SaaS, Okta leads in enterprise workforce identity, Amazon Cognito owns the AWS-native space, and Microsoft Entra ID owns Microsoft-centric workforce identity, while Authlete offers a middle path: a hosted protocol engine behind endpoints you run.

Full disclosure: we make Duende IdentityServer. This guide plays fair. Each product below links to a detailed, dated comparison, and every one of them is a reasonable choice for the teams it was designed for. The goal is to match a tool to your constraints, not to declare a universal winner.

This guide was last reviewed on September 10, 2026. All of these products are actively developed. Check the linked comparisons and vendor documentation for current details.

Which Identity Provider Is Best for Your Scenario?

  • Best for .NET teams that want full control: Duende IdentityServer. A standards-based identity server (OpenID Connect, OAuth, and SAML, plus a first-party user management layer) that runs in a dedicated ASP.NET Core identity host, with clients, claims, and UI as C# in your own solution, and commercial support behind it.
  • Best open-source .NET option: OpenIddict. A free, flexible library with the same hosting model, where you author the protocol endpoints yourself. Compared here.
  • Best free standalone server: Keycloak. A batteries-included Java server with an admin console, built-in login UI, and LDAP/AD federation. Compared here.
  • Best API-first standalone server: FusionAuth. A Java server with a comprehensive REST API, hosted login pages, built-in multi-tenancy, and a free self-hosted Community edition, with advanced features on paid plans. Compared here.
  • Best commercial standalone server: Curity Identity Server. A JVM server product with a large authenticator catalog, HAAPI for native apps, and packaged financial-grade compliance. Compared here.
  • Best managed SaaS for application identity: Auth0. Hosted login, a large connection catalog, and the fastest path to production, priced per monthly active user. Compared here.
  • Best for AWS-native teams: Amazon Cognito. User pools, identity pools, a managed login UI, and deep AWS integration, priced per monthly active user. Compared here.
  • Best for Microsoft-centric workforce identity: Microsoft Entra ID. Microsoft 365 SSO, Conditional Access, and device policies, frequently combined with Duende IdentityServer via federation. Compared here.
  • Best for enterprise workforce identity: Okta. A managed platform with 7,000+ app integrations, adaptive MFA, and automated lifecycle management. Compared here.
  • Best hosted protocol engine (financial-grade as a service): Authlete. FAPI-certified protocol logic as a REST API behind authorization-server endpoints you build and host. Compared here.

How Do These Identity Provider Categories Compare?

Category Examples You operate Best when

Managed SaaS

Auth0, Okta, Amazon Cognito, Microsoft Entra ID

Nothing (they host it)

You want identity as a service and accept per-user pricing and platform boundaries

Self-hosted OSS server

Keycloak

A Java server and database

You want a full-featured server with an admin UI and don’t mind operating the JVM

Self-hosted server (free tier)

FusionAuth

A Java server and database

You want an API-first server with hosted login pages and a free self-hosted tier, and accept plan-gated features

Self-hosted commercial server

Curity Identity Server

A Java server and database

You want a commercial server product with a large built-in authenticator catalog and financial-grade packaging

Hosted protocol engine

Authlete

Your authorization-server endpoints; the protocol logic runs as a REST API

You want protocol internals externalized, while you own the endpoints and user authentication

Self-hosted .NET framework

OpenIddict

An ASP.NET Core identity host (you author the protocol endpoints)

You want an OSS library and are happy to assemble the server plumbing yourself

Self-hosted .NET framework

Duende IdentityServer

An ASP.NET Core identity host (protocol endpoints built in)

You want a standards-based token server that is part of your .NET codebase and deployment, with full control and commercial support

OpenIddict and Duende IdentityServer sit in the same hosting category. Both are NuGet packages you host in an ASP.NET Core project, a dedicated identity host that is separate from the applications it secures. What separates them is how much of the token server the framework provides versus how much you assemble. The OpenIddict comparison covers that in detail.

What Does Running Duende IdentityServer Involve?

Your identity host is an ASP.NET Core application. It builds, deploys, and scales like any other ASP.NET Core app: run it behind a load balancer, scale out horizontally, containerize it, and ship it through your usual CI/CD. It runs as its own host, separate from the apps it secures, so it also needs the same production setup any shared ASP.NET Core service does. In particular, configure ASP.NET Core Data Protection with a shared, persisted key ring, a signing key store the whole cluster can reach, and distributed caching where it applies.

The deployment documentation walks through the full checklist.

Shared Vocabulary for the Comparisons

Every comparison includes a concept map from the source product to Duende IdentityServer. Four Duende terms come back in each one:

• Client: an application that requests tokens, such as a web app, SPA, mobile app, or machine-to-machine service. Whatever a product calls its app registrations, applications, or clients maps here.
• API resources and scopes: the APIs you protect and the permissions clients can request. Identity resources model the user-identity claims (such as profile and email) that go into ID tokens.
• IProfileService: the C# extensibility point that turns your user store’s data into token claims. Rules, actions, protocol mappers, and app roles all become IProfileService logic.
• Duende User Management: the first-party user layer, covering passkeys, TOTP, OTP, passwords, recovery codes, and bulk user import.

With those four in mind, the concept maps in the comparisons are easy to follow.

Should You Self-Host, Buy SaaS, or Build Your Own?

Before picking a specific product, settle the operating model: whether to self-host identity, buy a SaaS platform, or build your own. Who runs the token server, and how much of it you build yourself? These three decision frameworks work through that choice:

Where Can I Find Detailed Comparisons?

Further Reading