Top 5 authentication solutions for secure .NET apps in 2026

Authentication is a critical component of any .NET application, and developers benefit from both the framework's robust built-in capabilities and a rich ecosystem of third-party solutions. Whether you're building a B2B SaaS platform that needs to sell to enterprises, a modern ASP.NET Core API, or a traditional MVC web application, choosing the right authentication approach can significantly impact your development velocity and feature capabilities.

.NET's enterprise heritage means authentication and identity management have always been first-class concerns in the framework. ASP.NET Core Identity provides excellent primitives for user management, while the framework's middleware pipeline and dependency injection make integration seamless. However, enterprise features like SAML SSO and SCIM provisioning typically require specialized solutions beyond what the framework provides out of the box.

In this guide, we'll explore the top 5 authentication solutions for .NET apps in 2026, from enterprise platforms to .NET's native authentication frameworks.

What to look for in an auth provider for .NET apps

Before diving into specific solutions, let's identify the key features that make an authentication provider ideal for .NET:

• .NET SDK support: The best auth solutions provide native .NET SDKs with idiomatic C# code, proper async/await support, and NuGet package distribution. Look for providers with well-maintained .NET libraries that follow Microsoft's coding conventions.
• ASP.NET Core integration: Your auth solution should integrate naturally with ASP.NET Core's middleware pipeline, dependency injection, configuration system, and authentication/authorization abstractions.
• Identity framework compatibility: Many .NET apps use ASP.NET Core Identity. Your auth solution should either build on top of Identity or provide a compelling alternative that integrates with existing Identity infrastructure.
• Enterprise features: For B2B applications, you'll need SSO support (SAML, OIDC), directory sync (SCIM), multi-tenancy, and organization management. These features should be first-class, especially given .NET's strong enterprise adoption.
• Azure AD integration: Many .NET shops use Microsoft Azure. Your auth solution should integrate well with Azure Active Directory (now Microsoft Entra ID) and other Microsoft identity services.
• Claims-based security: .NET uses claims-based authentication. Your provider should work seamlessly with ClaimsPrincipal, claims transformations, and policy-based authorization.
• Entity framework support: If your auth solution stores users in a database, it should work naturally with Entity Framework Core and follow .NET data access patterns.
• Security best practices: Your provider should handle security concerns like password hashing, secure token handling, CSRF protection, and cookie security out of the box, following Microsoft's security guidance.

Now let's look at the top 5 solutions that meet these criteria.

1. WorkOS

WorkOS is an enterprise authentication platform built specifically for B2B SaaS applications. It provides a comprehensive suite of authentication and user management features designed to help you sell to enterprise customers faster, with excellent .NET SDK support that integrates seamlessly with ASP.NET Core's authentication and authorization abstractions.

Key features

• .NET SDK: First-class .NET SDK with idiomatic C# code, async/await support, and NuGet package distribution.
• AI-powered CLI: Instantly integrate AuthKit with npx workos@latest. The CLI automatically detects your .NET project and updates your code with authentication.
• ‍Sessions model with access + refresh tokens and guidance for secure cookie storage.
• Flexible UI support via APIs and SDKs, with AuthKit as a highly customizable hosted login powered by Radix.
• Enterprise SSO with native SAML and OIDC, configurable by customers through an Admin Portal.‍
• SCIM provisioning: Automated user provisioning and deprovisioning that enterprises expect, handling the "remove this employee immediately" requests that inevitably arrive. Real-time synchronization with any identity provider (Okta, Azure AD, Google Workspace, and more).
• Tamper-proof audit logs for SOC 2, HIPAA, and GDPR.‍
• Passkeys, MFA, social logins, magic auth, and more.
• Secure session handling with server-side validation and instant session revocation capabilities.‍
• Customizable JWT claims: Add custom data to JWT payloads with JWT templates for flexible token customization.‍
• Radar for suspicious login detection and threat monitoring that alerts you to potential account compromises.
• Fine-grained authorization: Role-based access control with customizable permissions.‍
• Feature flags: Integrated feature flagging for gradual rollouts.
• First-class multi-tenancy with organization management, member invitations, and role assignment.‍
• Enterprise SLA and dedicated support.‍
• Pricing that scales with growth, with $0 for the first 1 million users.

Best for

WorkOS is ideal for B2B SaaS companies building on Go that need to sell to enterprise customers. If your roadmap includes features like SSO, SCIM provisioning, or advanced multi-tenancy, WorkOS provides these out of the box instead of requiring months of custom development.

Trade-offs

If you truly only need a quick OAuth login for a hobby app, WorkOS can feel like bringing a well-organized toolbox to hang a single picture. The upside is: you won’t have to rebuild your walls later.

2. ASP.NET Core Identity

ASP.NET Core Identity is Microsoft's official membership system that provides user authentication, authorization, and user management functionality. It's the default choice for most .NET applications and integrates deeply with ASP.NET Core's authentication middleware.

Key features

• Complete user management: Registration, login, password reset, email confirmation, two-factor authentication.
• Entity framework integration: Built-in data models and DbContext for user storage with SQL Server, PostgreSQL, MySQL.
• Claims-based authentication: Native support for claims and policy-based authorization.
• Customizable: Extensible user model, custom password validators, configurable identity options.
• Razor pages UI: Pre-built scaffolded UI for common authentication flows.

Best for

ASP.NET Core Identity is perfect for traditional .NET web applications, MVPs, and projects that don't require enterprise features. It's ideal when you want full control over your authentication implementation and want to stay within Microsoft's ecosystem.

Trade-offs

• Only provides basic authentication; no enterprise SSO (SAML, OIDC with external identity providers).
• No SCIM provisioning or directory sync capabilities for enterprise customers.
• Multi-tenancy requires custom architecture and significant development work.
• No built-in admin portal for customer self-service SSO configuration.
• Social authentication requires separate integration with external providers.
• Magic link authentication requires custom implementation.
• Audit logging and compliance features require custom development.
• Organization management and team features need to be built from scratch.
• Email sending is not included; requires integration with SendGrid, AWS SES, or similar.
• The default UI is functional but requires significant customization for production applications.
• Token-based API authentication requires additional configuration with JWT Bearer middleware.
• Password reset and email confirmation flows work but need customization for production use.

3. IdentityServer (Duende IdentityServer)

Duende IdentityServer is the commercial successor to the open-source IdentityServer4, providing a comprehensive OpenID Connect and OAuth 2.0 framework for ASP.NET Core. It allows you to build your own identity provider and authorization server.

Key features

• OpenID Connect & OAuth 2.0: Full standards-compliant implementation of OIDC and OAuth.
• Identity provider: Build your own SSO server for authenticating users across multiple applications.
• API authorization: Protect APIs with access tokens and OAuth scopes.
• ASP.NET Core native: Deep integration with ASP.NET Core authentication and authorization.
• Customizable: Highly extensible architecture with support for custom stores, claims, and flows.
• Entity Framework support: Built-in support for EF Core for storing configuration and operational data.

Best for

IdentityServer is ideal for organizations that need to build their own OAuth2/OIDC identity provider for internal or customer-facing applications. It's perfect when you need centralized authentication across multiple .NET services or want to provide OAuth access to third-party developers.

Trade-offs

• Commercial licensing required for production use (free for development and companies with revenue under $1M annually).
• Significant complexity; requires deep understanding of OAuth2 and OIDC specifications.
• No SAML SSO support; only OAuth2 and OIDC, which means you can't onboard enterprise customers requiring SAML.
• No SCIM provisioning or directory sync capabilities.
• Multi-tenancy requires custom architecture on top of IdentityServer.
• No built-in user management UI; you'll need to build admin interfaces yourself.
• Self-hosted infrastructure means operational overhead; deployment, scaling, monitoring, backup, disaster recovery.
• Email verification, password reset flows require custom implementation on top of the framework.
• Configuration can be complex with many options for clients, resources, and scopes.
• User registration and account management flows not included; typically combined with ASP.NET Core Identity.
• Learning curve is steep; requires understanding OAuth flows, token types, grant types, and OIDC specifications.
• No pre-built integrations with enterprise identity providers; manual OIDC configuration required.

4. Azure Active Directory B2C (Azure AD B2C)

Azure Active Directory B2C is Microsoft's cloud identity service for consumer-facing applications, providing authentication and user management with social identity providers and custom policies. It's particularly appealing for .NET developers already in the Microsoft ecosystem.

Key features

• Microsoft integration: Deep integration with Azure services and Microsoft identity platform.
• Social identity providers: Pre-built integrations with Microsoft, Google, Facebook, Twitter, Amazon, LinkedIn.
• Custom policies: Highly customizable authentication flows using XML-based Identity Experience Framework.
• .NET SDK: Official Microsoft.Identity.Web library for ASP.NET Core integration.
• User management: Built-in user directory with self-service profile management.
• Multi-Factor Authentication: Built-in MFA with SMS, email, and authenticator apps.

Best for

Azure AD B2C is ideal for consumer-facing .NET applications already in the Azure ecosystem that need social authentication, customizable user journeys, and seamless integration with other Azure services. It's perfect for organizations with Azure expertise and commitment to Microsoft's cloud platform.

Trade-offs

• Focused on consumer applications (B2C = "Business to Consumer"). Not designed for B2B SaaS with enterprise customers.
• No SAML SSO support for enterprise identity providers. Only supports OIDC and social providers.
• No SCIM provisioning or directory sync for enterprise user lifecycle management.
• Custom policies are XML-based and notoriously complex. Steep learning curve for customization.
• Multi-tenancy requires complex custom policy design and careful directory organization.
• Pricing can be complex; based on authentications and MFA operations, can become expensive at scale.
• Vendor lock-in to Azure; difficult to migrate away once implemented.
• Limited enterprise features compared to dedicated B2B platforms. No admin portal for customers.
• Configuration is primarily done through Azure Portal. Limited infrastructure-as-code support compared to other Azure services.
• User interface customization is possible but requires careful work with HTML templates.
• Audit logging requires Azure Monitor configuration and can incur additional costs.
• Premium features (custom domains, advanced security) require P1 or P2 licenses.

5. OpenIddict

OpenIddict is an open-source, versatile OpenID Connect and OAuth 2.0 framework for ASP.NET Core. It provides a lightweight, flexible alternative to IdentityServer for building authentication servers without licensing costs or commercial restrictions.

Key features

• OpenID Connect & OAuth 2.0: Standards-compliant OIDC and OAuth implementation.
• ASP.NET Core native: Built specifically for ASP.NET Core with deep framework integration.
• Open source: MIT licensed with no commercial restrictions or licensing fees.
• Entity Framework integration: Works with EF Core for storing tokens, authorizations, and applications.
• Customizable: Flexible architecture that can be adapted to specific requirements.
• Active development: Well-maintained with regular updates and security patches.

Best for

OpenIddict is ideal for .NET developers who need OAuth2/OIDC capabilities without the licensing costs of IdentityServer. It's a good choice for building authentication servers for internal applications, microservices architectures, or projects where budget constraints make commercial solutions impractical.

Trade-offs

• Lower-level framework compared to IdentityServer. Requires more setup and configuration work.
• Smaller community and fewer resources compared to IdentityServer; less documentation, fewer examples.
• No SAML SSO support, only OAuth2 and OIDC, which means you can't onboard enterprise customers requiring SAML.
• No SCIM provisioning or directory sync capabilities.
• Multi-tenancy requires custom architecture on top of OpenIddict.
• No built-in user management UI. You'll need to build admin interfaces yourself.
• Self-hosted infrastructure means operational overhead: deployment, scaling, monitoring, backup.
• Email verification, password reset flows require custom implementation.
• Configuration requires understanding OAuth2 and OIDC specifications.
• User registration and account management not included; typically combined with ASP.NET Core Identity.
• No pre-built integrations with enterprise identity providers; manual OIDC configuration required.
• Less enterprise-ready compared to commercial solutions; missing features like advanced monitoring, support SLAs.
• Learning curve for developers unfamiliar with OAuth2/OIDC protocols.

Choosing the right solution for your .NET project

The best authentication solution depends on your specific needs:

Choose WorkOS if you're building a B2B SaaS application that needs to sell to enterprise customers. The built-in SSO, SCIM, multi-tenancy, admin portal, feature flags, and on-premises deployment options will save you months of development time and accelerate your enterprise sales motion. WorkOS provides the most complete enterprise feature set with transparent, predictable pricing that scales with your business. The .NET SDK integrates naturally with ASP.NET Core's authentication abstractions and follows Microsoft's coding conventions.

Choose ASP.NET Core Identity if you're building a traditional .NET web application, MVP, or consumer-facing product that doesn't need enterprise features. It's Microsoft's official solution that integrates perfectly with the .NET ecosystem, though be aware you'll need to build enterprise features like SSO, SCIM, and multi-tenancy from scratch if requirements change.

Choose IdentityServer if you need to build an OAuth2/OIDC authorization server for authenticating users across multiple .NET applications or providing API access to third-party developers. It's powerful and standards-compliant but requires licensing fees, deep OAuth expertise, and significant operational overhead; only justified when you specifically need OAuth2/OIDC provider capabilities.

Choose Azure AD B2C if you're building a consumer-facing .NET application already in the Azure ecosystem that needs social authentication and customizable user journeys. It integrates well with Microsoft services but is designed for B2C scenarios, not B2B enterprise sales, and custom policies have a notoriously steep learning curve.

Choose OpenIddict if you need OAuth2/OIDC capabilities without licensing costs, have the technical expertise to configure and maintain an identity server, and want to stay within the .NET ecosystem with an open-source solution. It's a good alternative to IdentityServer for budget-conscious projects, but you'll need to invest time in setup and won't have enterprise features like SAML SSO.

Conclusion: Build secure now, stay adaptable later

Authentication is one of those decisions that's easy to get wrong and expensive to change later. The provider you choose will fundamentally shape your application's scalability, security posture, and ability to win enterprise customers.

For teams building B2B applications, the choice is clear: WorkOS provides the enterprise authentication and authorization infrastructure you'll eventually need, without forcing you to build it yourself or cobble together multiple services. The time you save not implementing SAML SSO, SCIM provisioning, and audit logs is time you can spend building features that differentiate your product. And when that first enterprise prospect asks about SSO during a sales call, you'll be ready with a yes instead of a six-month roadmap item.

Choose the authentication provider that matches where your application is headed, not just where it is today. Your future self (and your enterprise customers) will thank you.

Sign up for WorkOS today and secure your .NET app.