How to: Authentication, Authorization, and User Management
* [360username](https://360username.com/) - A free tool to search a username across 90+ social platforms to find matching profiles.
  * [Aserto](https://www.aserto.com) - Fine-grained authorization as a service for applications and APIs. Free up to 1000 MAUs and 100 authorizer instances.
  * [asgardeo.io](https://wso2.com/asgardeo) - 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.
  * [Auth0](https://auth0.com/) — Hosted SSO. The free plan includes 25,000 MAUs, unlimited Social Connections, a custom domain, and more.
  * [Authgear](https://www.authgear.com) - Bring Passwordless, OTPs, 2FA, SSO to your apps in minutes. All Front-end included. Free up to 5000 MAUs.
  * [Authress](https://authress.io/) — Authentication login and access control, unlimited identity providers for any project. Facebook, Google, Twitter and more. The first 1000 API calls are free.
  * [Authy](https://authy.com) - Two-factor authentication (2FA) on multiple devices, with backups. Drop-in replacement for Google Authenticator. Free for up to 100 successful authentications.
  * [Cerbos Hub](https://www.cerbos.dev/product-cerbos-hub) - 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.
  * [Clerk](https://clerk.com) — User management, authentication, 2FA/MFA, prebuilt UI components for sign-in, sign-up, user profiles, and more. Free up to 10,000 monthly active users.
  * [Cloud-IAM](https://www.cloud-iam.com/) — Keycloak Identity and Access Management as a Service. Free up to 100 users and one realm.
  * [Descope](https://www.descope.com/) — Highly customizable AuthN flows, has both a no-code and API/SDK approach, Free 7,500 active users/month, 50 tenants (up to 5 SAML/SSO tenants).
  * [duo.com](https://duo.com/) — Two-factor authentication (2FA) for website or app. Free for ten users, all authentication methods, unlimited, integrations, hardware tokens.
  * [Kinde](https://kinde.com/) - Simple, robust authentication you can integrate with your product in minutes.  Everything you need to get started with 7,500 free MAU.
  * [logintc.com](https://www.logintc.com/) — Two-factor authentication (2FA) by push notifications, free for ten users, VPN, Websites, and SSH
  * [Logto](https://logto.io/) - Develop, secure, and manage user identities of your product - for both authentication and authorization. Free for up to 5,000 MAUs with open-source self-hosted option available.
  * [MojoAuth](https://mojoauth.com/) - MojoAuth makes it easy to implement Passwordless authentication on your web, mobile, or any application in minutes.
  * [Okta](https://developer.okta.com/signup/) — User management, authentication and authorization. Free for up to 100 monthly active users.
  * [Ory](https://ory.sh/) - AuthN/AuthZ/OAuth2.0/Zero Trust managed security platform. Forever free developer accounts with all security features, unlimited team members, 200 daily active users, and 25k/mo permission checks.
  * [Permit.io](https://permit.io) - 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.
  * [Phase Two](https://phasetwo.io) - Keycloak Open Source Identity and Access Management. Free realm up to 1000 users, up to 10 SSO connections, leveraging Phase Two's Keycloak enhanced container which includes the [Organization](https://phasetwo.io/product/organizations/) extension.
  * [PropelAuth](https://propelauth.com) — A Sell to companies of any size immediately with a few lines of code, free up to 200 users and 10k Transactional Emails (with a watermark branding: "Powered by PropelAuth").
  * [Stack Auth](https://stack-auth.com) — Open-source authentication that doesn't suck. The most developer-friendly solution, getting you started in just five minutes. Self-hostable for free, or offers a managed SaaS version with 10k free Monthly Active Users.
  * [Stytch](https://www.stytch.com/) - An all-in-one platform that provides APIs and SDKs for authentication and fraud prevention. The free plan includes 10,000 monthly active users, unlimited organizations, 5 SSO or SCIM connections, and 1,000 M2M tokens.
  * [SuperTokens](https://supertokens.com/) - 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.
  * [WorkOS](https://workos.com/) - Free user management and authentication for up to 1 Million MAUs. Support email + password, social auth, Magic Auth, MFA, and more.
  * [ZITADEL Cloud](https://zitadel.com) — A turnkey user and access management that works for you and supports multi-tenant (B2B) use cases. Free for up to 25,000 authenticated requests, with all s