Keycloak is itself open source (Apache-2.0), an identity and access management server offering user federation, strong authentication, user management and fine-grained authorisation. Teams look at alternatives when they want a lighter footprint, a friendlier admin experience, a headless API-first design, or a tighter fit for a reverse proxy or Kubernetes.
Every tool below is under an OSI-approved licence (MIT, Apache-2.0, AGPL-3.0 or MPL-2.0), checked against its repository. Several are open-core, so enterprise-only parts are called out in each entry.
Licences checked against each repository on November 7, 2026.
1. authentik
MITBest for: Friendly all-round identity provider
An open-source identity provider for modern SSO, designed for self-hosting from small labs to large production clusters. Supports SAML, OAuth2/OIDC, LDAP and RADIUS, and deploys with Docker Compose, Helm on Kubernetes, AWS CloudFormation or DigitalOcean.
Strengths
- + Broad protocol support including SAML, OIDC, LDAP and RADIUS
- + Docker Compose and Helm deployments
- + Proxy-style authentication for apps
Trade-offs
- − The authentik/enterprise directory is under a separate licence
- − Runs as several services
2. ZITADEL
AGPL-3.0Best for: Multi-tenant identity for SaaS products
An open-source identity and access management platform for teams that need more than basic auth. Offers certified OpenID Connect, SAML 2.0, SCIM 2.0, passkeys and MFA, multi-tenancy with organisations, and gRPC and REST APIs. Needs PostgreSQL 14 or later.
Strengths
- + Multi-tenant model of instances, organisations and projects
- + Audit event stream and SIEM integration
- + Docker Compose and Kubernetes deployment
Trade-offs
- − AGPL-3.0 with some Apache-2.0 and MIT directories; see LICENSING.md
- − Requires PostgreSQL
3. Ory Kratos
Apache-2.0Best for: Headless, API-first user management
Headless cloud-native authentication and identity management written in Go. Provides self-service login, registration, verification and recovery, MFA and passkeys, driven through APIs. Works with PostgreSQL, MySQL or CockroachDB.
Strengths
- + API-first design you build your own UI on
- + Passkeys, social sign-in, OIDC, magic links and TOTP
- + Runs on Linux, macOS, Windows or Docker
Trade-offs
- − No ready-made admin UI; you build the front end
- − SCIM, SAML and organisation SSO need the Ory Enterprise License
4. Authelia
Apache-2.0Best for: SSO and 2FA in front of a reverse proxy
An open-source authentication and authorisation server providing two-factor authentication and SSO through a web portal. Works with reverse proxies such as nginx, Traefik, Caddy, Envoy and HAProxy, and is OpenID Certified.
Strengths
- + Fine-grained access rules by user, group, URI and network
- + OpenID Connect and WebAuthn passkeys
- + Docker, Kubernetes and static binary installs
Trade-offs
- − Built around protecting apps behind a proxy, not full user lifecycle management
- − Lite bundle uses file-based user storage
5. Casdoor
Apache-2.0Best for: Lightweight SSO server with a web console
A single sign-on and authentication server with a web console. Supports OAuth 2.0, OIDC, SAML 2.0, CAS, LDAP and SCIM 2.0, WebAuthn and MFA, and uses Casbin for access control. Install with Docker, Docker Compose or Helm.
Strengths
- + Wide protocol coverage
- + Web-based configuration with no redeploy
- + SDKs and REST API with Swagger UI
Trade-offs
- − The all-in-one Docker image is not meant for production
- − Docker Compose builds from source, so first start is slow
6. Logto
MPL-2.0Best for: Auth for SaaS apps with ready-made sign-in
The modern, open-source auth infrastructure for SaaS and AI apps, handling OIDC and OAuth 2.1 with pre-built, customisable sign-in flows. Offers multi-tenancy, enterprise SSO, RBAC and SDKs for 30+ frameworks. Self-host with Docker Compose or Node.js and PostgreSQL.
Strengths
- + Pre-built sign-in flows and SDKs
- + Multi-tenancy, enterprise SSO and RBAC
- + Docker Compose and Node.js install options
Trade-offs
- − MPL-2.0 is file-level copyleft
- − Needs PostgreSQL
7. SuperTokens
Apache-2.0Best for: Embedding login and sessions in your own app
An open-source auth provider adding secure login and session management to apps, positioned as an open-core alternative to proprietary providers. Supports passwordless, social and email/password login, MFA, multi-tenancy and a user management dashboard. Runs on-premises via Docker or binary.
Strengths
- + Session management and multiple login methods
- + User management dashboard
- + You keep user data in your own database
Trade-offs
- − Content under ee/ is covered by a separate licence
- − Backend core is Java, so budget JVM memory
8. Dex
Apache-2.0Best for: OIDC federation, especially for Kubernetes
An identity service that uses OpenID Connect to authenticate users for other applications, acting as a portal to upstream providers through connectors such as LDAP, GitHub, GitLab, Google, Microsoft and SAML 2.0. Runs on Kubernetes, in Docker or from source.
Strengths
- + Connectors to many upstream identity systems
- + Integrates with Kubernetes API-server authentication
- + Small and focused
Trade-offs
- − A federation layer, not a user database with admin UI
- − Connector stability varies
