Top 5 authentication solutions for secure FastAPI apps in 2026

Authentication is a critical component of any FastAPI application, and developers need solutions that work seamlessly with FastAPI's async architecture and automatic API documentation. Whether you're building a B2B SaaS platform that needs to sell to enterprises, a high-performance REST API, or a modern web application, choosing the right authentication approach can significantly impact your development velocity and feature capabilities.

FastAPI's modern, async-first design and automatic OpenAPI documentation make it ideal for building high-performance APIs, but the framework intentionally stays lightweight on authentication. While FastAPI provides excellent security utilities and OAuth2 schemes out of the box, enterprise features like SAML SSO and SCIM provisioning require specialized solutions. The framework's flexibility allows seamless integration with both FastAPI-native packages and external authentication providers.

In this guide, we'll explore the top 5 authentication solutions for FastAPI apps in 2026, from enterprise platforms to FastAPI's most popular authentication libraries.

What to look for in an auth provider for FastAPI apps

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

• Async support: FastAPI is built on async/await. Your auth solution should work seamlessly with async endpoints and not block the event loop with synchronous operations.
• OpenAPI integration: FastAPI automatically generates OpenAPI documentation. Your auth provider should integrate with FastAPI's security schemes so authentication appears correctly in the interactive docs.
• Dependency injection: FastAPI's dependency injection system is powerful. Your auth solution should leverage dependencies for authentication checks rather than decorators or middleware patterns from other frameworks.
• 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, not afterthoughts.
• Type safety: FastAPI developers use Pydantic and type hints extensively. Your auth provider should have excellent type hints and Pydantic model integration.
• Performance: FastAPI is chosen for performance. Your auth solution should be async-native and not introduce significant latency through synchronous database calls or blocking operations.
• API-first design: FastAPI is primarily for building APIs. Your auth solution should excel at token-based authentication (JWT, OAuth2) rather than just session-based approaches.
• Security best practices: Your provider should handle security concerns like password hashing with bcrypt/argon2, secure token handling, token rotation, and CORS configuration out of the box.

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 Python SDK support that integrates seamlessly with FastAPI's async architecture.

Key features

• Python SDK: First-class Python SDK that works naturally with FastAPI's async patterns.
• 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 FastAPI 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. FastAPI Users

FastAPI Users is the most popular authentication library specifically built for FastAPI. It provides a complete authentication system with user management, including registration, login, password reset, and email verification, all designed to work seamlessly with FastAPI's patterns.

Key features

• FastAPI-native: Built specifically for FastAPI with full async support and dependency injection.
• Multiple database support: Works with SQLAlchemy, MongoDB, Beanie ORM, and Tortoise ORM.
• OAuth integration: Pre-built OAuth2 authentication with popular providers (Google, GitHub, etc.).
• JWT and cookie authentication: Supports both stateless JWT tokens and session cookies.
• User management: Complete user CRUD operations with email verification and password reset.

Best for

FastAPI Users is a good choice for applications that need comprehensive user management and authentication without requiring enterprise features. It's ideal when you want a FastAPI-native solution that handles the common authentication patterns most applications need.

Trade-offs

• No enterprise SSO support (SAML, OIDC with external identity providers); only OAuth-based social login.
• 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.
• Audit logging and compliance features require custom implementation.
• Organization management and team features need to be built from scratch.
• While highly flexible, the library requires understanding multiple concepts (user manager, authentication backend, strategy).
• Magic link authentication requires custom implementation on top of the base library.
• No built-in rate limiting or bot detection; must be implemented separately.
• Email sending is not included; requires integration with email service providers.

3. Authlib

Authlib is a comprehensive Python library for OAuth 1.0/2.0 and OpenID Connect, providing both client and server implementations. It's framework-agnostic but integrates well with FastAPI for building OAuth providers or consuming OAuth services.

Key features

• OAuth 2.0 Server: Complete OAuth2 authorization server implementation.
• OAuth 2.0 Client: Consume OAuth services from providers like Google, GitHub, Microsoft.
• OpenID Connect: Full OIDC support for both client and server.
• JWT Support: Create, sign, and verify JSON Web Tokens.
• Async Support: Works with async frameworks like FastAPI.

Best for

Authlib is ideal when you need to build an OAuth2 authorization server in FastAPI, or when you need to integrate with multiple OAuth providers as a client. It's perfect for developers who need standards-compliant OAuth/OIDC implementation and want more control than higher-level libraries provide.

Trade-offs

• Lower-level library that requires more setup and understanding of OAuth2/OIDC specifications.
• No enterprise SSO support (SAML); focuses on OAuth2 and OIDC only.
• No SCIM provisioning or directory sync capabilities.
• Multi-tenancy and organization management require completely custom implementations.
• No built-in user management, registration flows, or password reset functionality.
• No admin dashboard or user management UI; you'll need to build these yourself.
• Database integration is manual; no pre-built models or ORM integration.
• Email verification, password hashing, and user CRUD operations must be implemented separately.
• Steeper learning curve compared to higher-level authentication libraries.
• Documentation assumes deep understanding of OAuth2 and OIDC specifications.

4. FastAPI Security

FastAPI Security encompasses FastAPI's built-in security utilities combined with popular third-party libraries for implementing authentication. This includes FastAPI's OAuth2 schemes, security dependencies, and integration with libraries like python-jose for JWT handling and passlib for password hashing.

Key features

• Built-in OAuth2 schemes: FastAPI's native OAuth2PasswordBearer and OAuth2AuthorizationCodeBearer
• Security dependencies: Use FastAPI's dependency injection for authentication checks
• OpenAPI integration: Automatic security documentation in interactive API docs
• JWT handling: Integration with python-jose or pyjwt for token creation and validation
• Password hashing: Use passlib with bcrypt or argon2 for secure password storage

Best for

FastAPI Security is a solid choice for developers who want maximum control and flexibility, prefer to assemble their own authentication stack from libraries, and have the expertise to implement security correctly.

Trade-offs

• Requires assembling and integrating multiple libraries yourself (python-jose, passlib, databases).
• No enterprise SSO support (SAML, OIDC with external identity providers).
• No SCIM provisioning or directory sync capabilities.
• All user management, registration, password reset flows must be built from scratch.
• Multi-tenancy and organization management require completely custom implementations.
• No built-in email verification, password reset tokens, or account management.
• No admin dashboard, user management UI, or pre-built components.
• Security vulnerabilities are your responsibility; must stay current with library updates.
• Database models, migrations, and user CRUD operations must be implemented manually.
• Token refresh logic, session management, and concurrent login handling require custom code.
• Time-consuming setup means slower time-to-market compared to comprehensive libraries.
• No magic links, social authentication, or passwordless flows without additional libraries.

5. Supabase Auth

Supabase Auth is part of the larger Supabase platform, providing authentication alongside a PostgreSQL database, storage, and real-time subscriptions. While not FastAPI-specific, it integrates with FastAPI applications through its REST API and Python client library.

Key features

• Multiple auth methods: Email/password, magic links, OAuth providers, and phone authentication.
• Row level security: Database-level security policies that integrate with authentication.
• Python client: Official Python client library for backend integration.
• Open source: Self-hostable for compliance or data residency requirements.
• Integrated platform: Seamless integration with Supabase database, storage, and edge functions.

Best for

Supabase Auth is perfect for startups and indie developers building FastAPI applications who want an integrated backend platform and don't mind stepping outside FastAPI's ecosystem. If you're already using or planning to use PostgreSQL and want real-time features, Supabase's integrated approach can speed up development. However, should you need enterprise features be prepared to build everything from scratch.

Trade-offs

• No enterprise features like SAML SSO or SCIM provisioning; unsuitable for B2B SaaS targeting enterprise customers.
• Platform approach creates vendor lock-in; authentication tightly coupled to Supabase infrastructure.
• Multi-tenancy requires significant custom architecture with database schemas, row-level security policies, and application-level tenant isolation.
• Integration feels less natural than FastAPI-native packages. Uses REST API instead of FastAPI's dependency injection and async patterns.
• No FastAPI-specific package—requires HTTP requests through Python client library, resulting in more boilerplate.
• Session management doesn't leverage FastAPI patterns. Must manage JWT tokens manually.
• Admin dashboard is basic; requires custom tooling for advanced user management.
• JavaScript-first documentation means examples often need translation for FastAPI/Python use cases.
• Row Level Security (RLS) policies are PostgreSQL-specific and don't align with FastAPI's dependency system.
• Issues with any Supabase service (database, auth, storage) can impact your entire application.

Choosing the right solution for your FastAPI 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 async Python SDK integrates naturally with FastAPI's patterns and conventions.

Choose FastAPI Users if you're building a FastAPI application that needs comprehensive user management and authentication but doesn't require enterprise features. It's the most popular FastAPI-native authentication library with excellent documentation, though be aware you'll need to build enterprise features like SSO and SCIM from scratch if requirements change.

Choose Authlib if you need to build an OAuth2/OIDC authorization server or integrate with multiple OAuth providers, and you have the expertise to work with lower-level OAuth specifications. It's powerful and standards-compliant but requires more setup than higher-level libraries, and you won't have enterprise features like SAML SSO or user management UI.

Choose FastAPI Security (DIY approach) if you want maximum control and flexibility, have strong security expertise, and prefer to assemble your authentication stack from individual libraries. This gives you complete control but requires significant development time and ongoing security maintenance. Not recommended for teams that need to ship quickly or lack dedicated security resources.

Choose Supabase Auth if you're building a startup or indie project that doesn't need enterprise features, and you want an integrated backend platform outside FastAPI's ecosystem. Be prepared for less idiomatic FastAPI integration and vendor lock-in to Supabase's infrastructure.

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 FastAPI app.