Open-source Duo Security alternatives

Keycloak is an open-source identity and access management server. It lets application teams add authentication and secure services without building their own login system, since Keycloak handles storing users and authenticating them. The project is written in Java, released under the Apache-2.0 license and governed under the Cloud Native Computing Foundation code of conduct.

Keycloak supports standard protocols such as OpenID Connect and SAML, and offers user federation, strong authentication, user management and fine-grained authorization. You can run it from the downloadable distribution using a start-dev command, or use the official Docker image published on Quay for containers and Kubernetes setups. The project provides documentation, a user mailing list and community channels for help, along with guidance for building and testing from source.

Authelia is an open-source authentication and authorization server that provides single sign-on and multi-factor authentication for web applications. It sits in front of your services, usually alongside a reverse proxy, so users sign in once at a portal and are checked against policies before reaching an app.

Supported factors and backends include TOTP, push notifications, two-factor methods and LDAP, according to its topics, and it is described as OpenID Certified and ready for post-quantum cryptography. It is written in Go and runs well as a small container, with documentation for Docker and Kubernetes deployments. Self-hosters often use it to add a consistent login and second factor to tools that have weak or no authentication of their own.

Authelia is licensed under Apache-2.0. As an authentication component, it is meant to be run on your own infrastructure, and it suits home labs, small organizations and teams wanting a lightweight identity layer without a heavier enterprise identity platform.

authentik is an open-source Identity Provider for modern single sign-on. It supports SAML, OAuth2 and OpenID Connect, LDAP, RADIUS and more, and is designed for self-hosting at any scale, from a small lab to production clusters. A reverse-proxy mode also lets it protect applications that lack native SSO support.

The project positions its enterprise offering as a way for organizations to replace incumbent identity providers (Okta, Auth0, Entra ID or Ping Identity) in large-scale identity management. For installation, Docker Compose is recommended for small and test setups, a Helm chart for Kubernetes suits larger setups, and official templates exist for AWS CloudFormation and a one-click DigitalOcean Marketplace app.

The codebase is mostly Python with Kubernetes tooling, and the license is listed as 'Other' on GitHub because it mixes open-source and enterprise components, so check which features fall under which terms. authentik is a common choice for self-hosters and companies who want to centralize logins across internal tools without paying per-user fees to a hosted identity vendor.

Aegis Authenticator is an open-source two-factor authentication app for Android. It generates one-time codes for online accounts and was created to offer features missing from other authenticator apps, notably proper encryption of the token store and reliable backups.

It supports the HOTP and TOTP algorithms, so it works with thousands of services and is compatible with Google Authenticator. The vault is encrypted with AES-256-GCM and can be unlocked with a password protected by scrypt or with biometrics through the Android Keystore. Extra protections include screen capture prevention and tap-to-reveal codes. Entries can be added by scanning a QR code, from an image or manually, and imported from apps such as Authy, andOTP, FreeOTP and Google Authenticator.

Aegis is written in Java and released under GPL-3.0. Entries can be organized with groups, custom icons and search, and the interface offers Light, Dark and AMOLED themes. Vaults can be exported in plaintext or encrypted form and backed up automatically. The app is distributed through Google Play and F-Droid, and the documentation describes its security design.

privacyIDEA is an open-source authentication server that manages multi-factor authentication for an organization. It issues and verifies second factors such as one-time passwords, hardware tokens, push notifications and FIDO2 or WebAuthn security keys, so applications and servers can add two-factor login without each building its own token handling.

The server is written in Python and exposes an API that other systems can call to check a login attempt. Its topics point to support for OTP, passkeys, push authentication and certificates, and administrators enroll and manage tokens centrally rather than configuring every service by hand. The project documentation includes how-tos for running it behind Apache2 with MySQL and for protecting a whole server farm.

privacyIDEA is released under the AGPL-3.0 licence and can be self-hosted, which keeps token data and user policies on infrastructure you control. The project website also lists an Enterprise Edition next to the community version, along with a demo site, screenshots and community resources for anyone evaluating it.