duo.com

Seamless Integration of SSO, MFA, passwordless auth and more. Includes SDKs for frontend and backend apps. Free up to 1000 MAUs and five identity providers.

Open source user authentication that natively integrates into your app - enabling you to get started quickly while controlling the user and developer experience. Free for up to 5000 MAUs.

Auhtorization-as-a-service provider platform enabling RBAC, ABAC, and ReBAC for scalable microservices with real-time updates and a no-code policy UI. A 1000 Monthly Active User free tier.

MojoAuth makes it easy to implement Passwordless authentication on your web, mobile, or any application in minutes.

Two-factor authentication (2FA) by push notifications, free for ten users, VPN, Websites, and SSH

Keycloak Identity and Access Management as a Service. Free up to 100 users and one realm.

A complete authorization management system for authoring, testing, and deploying access policies. Fine-grained authorization and access control, free up to 100 monthly active principals.

Free user management and authentication for up to 1 Million MAUs. Support email + password, social auth, Magic Auth, MFA, and more.