FusionAuth

FusionAuth is an enterprise-grade, developer-first customer identity and access management (CIAM) and user authentication platform that can be deployed anywhere—from customer-managed Docker containers and on-premises bare metal to fully managed cloud environments. Designed to provide software engineering teams with complete architectural freedom and data sovereignty, FusionAuth eliminates the rigid vendor lock-in, data hosting restrictions, and skyrocketing per-user pricing common to legacy identity SaaS vendors. The platform delivers a complete suite of identity features, including single sign-on (SSO), multi-factor authentication (MFA), passwordless authentication (Passkeys/WebAuthn, magic links), user registration forms, and social logins. FusionAuth supports standard identity federation protocols including OAuth 2.0, OpenID Connect (OIDC), and SAML v2, allowing developers to secure web applications, mobile apps, and microservice APIs with ease. FusionAuth includes an extensible JavaScript lambda engine, enabling custom token manipulation, custom password hashing algorithms, and dynamic user migration from legacy authentication systems without forcing users to reset their passwords. Scalable to hundreds of millions of users, FusionAuth delivers fast, flexible, and cost-effective authentication infrastructure that protects customer data and ensures regulatory compliance.