Open Source Authentication in 2026: Complete Comparison

Last updated: March 2026

The open-source identity and access management landscape has matured considerably. In 2020, Keycloak was essentially the only production-grade open-source IAM solution. By 2026, teams have several credible options. Each has different strengths, and the right choice depends on your architecture, team expertise, and feature requirements.

This comparison covers seven open-source authentication platforms in depth: Keycloak, Authentik, Zitadel, Ory (Hydra + Kratos), Gluu, Casdoor, and Logto. We evaluate each on architecture, features, community, and hosting options to help you make an informed decision.

The Comparison Table

Here is the high-level view before we dive into each solution:

Solution	Language	License	First Release	Protocol Support	Self-Host Complexity	Cloud Offering
Keycloak	Java (Quarkus)	Apache 2.0	2014	OIDC, SAML, OAuth 2.0	Medium	Managed (Skycloak, others)
Authentik	Python + Go	MIT (core)	2020	OIDC, SAML, LDAP, SCIM	Medium	authentik Cloud
Zitadel	Go	Apache 2.0	2020	OIDC, SAML, OAuth 2.0	Low	Zitadel Cloud
Ory (Hydra + Kratos)	Go	Apache 2.0	2016	OAuth 2.0, OIDC	High	Ory Network
Gluu	Java	Apache 2.0 / Gluu	2009	OIDC, SAML, UMA, FIDO	High	Gluu Cloud
Casdoor	Go	Apache 2.0	2021	OIDC, SAML, OAuth 2.0	Low	Casdoor Cloud
Logto	TypeScript	MPL 2.0	2022	OIDC, OAuth 2.0	Low	Logto Cloud

Keycloak

Keycloak is the enterprise standard for open-source IAM. Originally developed by Red Hat (now part of IBM), it has the largest community, the most extensive feature set, and the deepest enterprise integration of any open-source IAM solution.

Architecture

Keycloak runs on Quarkus (since version 17, replacing the older WildFly-based architecture). It uses an RDBMS for storage (PostgreSQL is recommended for production; H2 for development). Clustering is handled via Infinispan for session replication and cache distribution.

• Runtime: Quarkus (GraalVM-compatible)
• Database: PostgreSQL, MySQL, MariaDB, Oracle, MS SQL
• Clustering: Infinispan (embedded)
• Extension model: Service Provider Interfaces (SPIs) — Java-based extensions
• Admin interface: React-based Admin Console + Admin REST API

Key Strengths

• Protocol completeness: Full OIDC, SAML 2.0, and OAuth 2.0 support including edge cases like SAML IdP-initiated flow, OIDC backchannel logout, and DPoP
• Enterprise features: User federation (LDAP, Active Directory, custom), identity brokering, fine-grained authorization (UMA), organizations, custom authentication flows
• Extension ecosystem: Hundreds of community SPIs for custom authentication, event processing, and integration. The SPI architecture allows overriding almost any behavior
• Themes: Complete template-based theming with Freemarker or React (Keycloakify)
• Maturity: 10+ years of production use, backed by Red Hat/IBM
• Community: The largest open-source IAM community with active GitHub discussions, mailing lists, and a Discourse forum

Considerations

• Java expertise: Custom SPIs require Java development
• Resource usage: Java-based, so it requires more memory than Go-based alternatives (expect 512MB-1GB per instance minimum)
• Admin UI complexity: The Admin Console is powerful but has a learning curve

Managed Hosting

For teams that want Keycloak without the operational overhead, Skycloak provides fully managed Keycloak instances with automatic updates, monitoring, and enterprise SLAs. See our pricing page for details.

For self-hosting, use our Docker Compose Generator to create a production-ready deployment configuration, or follow our guide on deploying Keycloak in Kubernetes with ArgoCD.

Authentik

Authentik is a Python and Go-based identity provider that positions itself as an alternative to commercial solutions like Okta and Auth0. It has gained traction particularly in the homelab and self-hosting communities.

Architecture

Authentik uses a hybrid architecture: the core server is Python (Django), while the outpost proxy is written in Go. It uses PostgreSQL for storage and Redis for caching and task queuing.

• Runtime: Python (Django) + Go (outposts)
• Database: PostgreSQL only
• Cache: Redis
• Extension model: Policies (Rego, expression-based), Flows (visual designer)
• Admin interface: Web UI with visual flow designer

Key Strengths

• Flow designer: Visual authentication flow editor that makes complex flows accessible without code
• Proxy/forward auth: Built-in reverse proxy authentication (outpost mode) for protecting applications that cannot integrate OIDC/SAML natively
• LDAP outpost: Can expose its user directory as an LDAP server, useful for legacy applications
• Modern UI: Clean, modern admin interface with good UX
• SCIM support: Built-in SCIM provisioning

Considerations

• Smaller community: Active but smaller than Keycloak. Fewer third-party integrations and extensions
• Python performance: The Django core has higher latency than Go-based alternatives for authentication requests
• Enterprise features: Less mature fine-grained authorization compared to Keycloak
• SAML support: Functional but less battle-tested than Keycloak’s SAML implementation
• Extension model: Less flexible than Keycloak’s SPI system for deep customization

Zitadel

Zitadel is a Go-based identity platform focused on cloud-native architecture and developer experience. It is one of the newer entrants but has gained traction quickly.

Architecture

Zitadel is a single binary written in Go. It uses an event-sourced architecture, meaning all state changes are stored as events in the database, and current state is projected from those events. It supports CockroachDB and PostgreSQL.

• Runtime: Go (single binary)
• Database: CockroachDB, PostgreSQL
• Architecture: Event-sourced (CQRS)
• Extension model: Actions (JavaScript/TypeScript functions)
• Admin interface: Web Console + gRPC/REST APIs

Key Strengths

• Multi-tenancy: Built-in organizations and projects model, designed for B2B SaaS from the start
• Developer experience: Clean APIs, good documentation, and client libraries for many languages
• Low resource usage: Single Go binary with minimal memory footprint
• Event sourcing: Full audit trail built into the architecture
• Actions: JavaScript/TypeScript hooks for custom logic without deploying extensions
• Machine-to-machine: First-class support for service accounts and API keys

Considerations

• Younger project: Less battle-tested in large enterprise environments
• SAML support: Added later and less mature than Keycloak
• User federation: No built-in LDAP/AD federation (requires external sync)
• Theme customization: Less flexible than Keycloak’s theming system
• Event sourcing complexity: The event-sourced architecture can be harder to debug and maintain

Ory (Hydra + Kratos)

Ory takes a microservices approach to identity: instead of one monolithic IAM server, it provides separate Go services for different concerns.

Architecture

• Ory Hydra: OAuth 2.0 and OpenID Connect server (certified by the OpenID Foundation)
• Ory Kratos: User management and self-service flows (registration, login, password reset)
• Ory Oathkeeper: API gateway and access proxy
• Ory Keto: Authorization service (Google Zanzibar-inspired permission system)

Each component is a standalone Go binary with its own database.

• Runtime: Go (multiple services)
• Database: PostgreSQL, MySQL, CockroachDB
• Extension model: Webhooks, JSON-based configuration
• Admin interface: Minimal (API-first, use Ory Console for hosted version)

Key Strengths

• Composable architecture: Use only the components you need
• Hydra’s OIDC certification: One of the few open-source OIDC servers with OpenID Foundation certification
• Keto for authorization: Google Zanzibar-inspired permission system for ReBAC
• Bring your own UI: Kratos does not provide a login UI; you build your own, giving full design control
• Performance: Go-based, minimal resource usage per component

Considerations

• Operational complexity: Running 3-4 separate services is significantly more complex than a single IAM server
• No built-in UI: You must build your own login/registration pages (pro or con depending on your perspective)
• No SAML support: Hydra only supports OIDC/OAuth 2.0. SAML requires a separate solution
• No admin console: No built-in admin UI for the self-hosted version
• Integration effort: Wiring the components together requires significant configuration

Gluu

Gluu is one of the oldest open-source IAM projects, predating Keycloak. It focuses on enterprise identity and has strong FIDO/WebAuthn support.

Architecture

Gluu 5 (Jans) is built on the Janssen Project, a Linux Foundation project. It uses a microservices architecture with components for authentication, authorization, FIDO, and SCIM.

• Runtime: Java (microservices)
• Database: MySQL, PostgreSQL, Couchbase, LDAP
• Extension model: Jython scripts (Python syntax on JVM)
• Admin interface: Flex Admin UI

Key Strengths

• FIDO certification: Strong FIDO2/WebAuthn support, FIDO Alliance certified
• UMA support: Full User-Managed Access 2.0 implementation
• Compliance focus: Designed for regulated industries
• SCIM: Built-in SCIM 2.0 server
• History: Longest track record among open-source IAM solutions

Considerations

• Complexity: The most complex self-hosting experience of any solution listed here
• Community size: Smaller active community compared to Keycloak or Authentik
• Documentation: Can be difficult to navigate
• Licensing: Some components have different licenses (open-core model)
• Learning curve: Jython-based customization has a steep learning curve

Casdoor

Casdoor is a Go-based identity platform that aims to be a simpler alternative to Keycloak, with a focus on the Chinese market and international expansion.

Architecture

Casdoor is a single Go binary with a React frontend. It uses standard RDBMS for storage.

• Runtime: Go + React
• Database: MySQL, PostgreSQL, SQLite, MS SQL
• Extension model: Webhooks, plugins
• Admin interface: React-based web UI

Key Strengths

• Simplicity: Easy to deploy and configure
• Social login breadth: Supports a very large number of social login providers, including Chinese providers (WeChat, DingTalk, Lark)
• Multi-language: Internationalized UI with strong CJK support
• Low resource usage: Single Go binary

Considerations

• Enterprise features: Limited fine-grained authorization, no UMA
• SAML: Basic SAML support
• Community: Growing but small outside of China
• Documentation: Quality varies; much content is translated from Chinese
• User federation: No LDAP/AD federation
• Maturity: Newer project, less battle-tested

Logto

Logto is a TypeScript-based auth platform that positions itself as an open-source Auth0 alternative with a focus on developer experience.

Architecture

Logto is built entirely in TypeScript (Node.js backend, React frontend). It targets developers building consumer-facing applications.

• Runtime: Node.js (TypeScript)
• Database: PostgreSQL
• Extension model: Webhooks, connectors
• Admin interface: Modern React-based console

Key Strengths

• Developer experience: The best developer experience and documentation of any solution listed here
• Modern stack: TypeScript throughout, modern React UI
• Pre-built UI components: Drop-in sign-in experience (similar to Clerk/Auth0)
• Connectors: Pluggable social login and SMS/email connectors
• Machine-to-machine: Built-in API resource management

Considerations

• No SAML support: OIDC/OAuth 2.0 only
• No user federation: No LDAP/AD integration
• Enterprise features: Limited RBAC, no fine-grained authorization
• Node.js performance: Higher latency compared to Go-based solutions under load
• Newer project: Less proven at scale

Feature Comparison Matrix

Feature	Keycloak	Authentik	Zitadel	Ory	Gluu	Casdoor	Logto
OIDC	Full	Full	Full	Full (certified)	Full	Full	Full
SAML 2.0	Full	Yes	Yes	No	Full	Basic	No
OAuth 2.0	Full	Yes	Yes	Full	Full	Yes	Yes
LDAP Federation	Yes	Outpost	No	No	Yes	No	No
SCIM	Via extension	Yes	Yes	No	Yes	No	No
MFA (TOTP)	Yes	Yes	Yes	Yes	Yes	Yes	Yes
WebAuthn/Passkeys	Yes	Yes	Yes	Yes	Yes (FIDO certified)	Basic	Yes
Social Login	20+	20+	15+	Build your own	10+	50+	20+
Custom Themes	Full	Yes	Limited	Build your own	Limited	Yes	Pre-built
Fine-grained Authz	UMA + policies	Policies	No	Keto (ReBAC)	UMA	No	Basic RBAC
Organizations	Yes (v25+)	No	Yes	No	No	Yes	Yes
Event Streaming	SPI-based	Webhooks	Actions	Webhooks	Jython	Webhooks	Webhooks
Admin API	REST	REST	gRPC + REST	REST	REST	REST	REST

For details on Keycloak’s feature capabilities, explore our feature pages: SSO, MFA, RBAC, Identity Providers, SCIM, Audit Logs, Session Management, Branding, and Insights.

Community and Ecosystem Comparison

Metric	Keycloak	Authentik	Zitadel	Ory (combined)	Gluu	Casdoor	Logto
GitHub Stars (approx.)	25k+	14k+	10k+	15k+	1.5k+	10k+	9k+
Contributors	1,000+	300+	200+	300+	100+	200+	100+
First Commit	2013	2019	2020	2015	2009	2021	2022
Backing	Red Hat/IBM	authentik Security	Zitadel AG	Ory Corp	Gluu Inc	Casbin	Silverhand
Extension Ecosystem	Large (SPIs)	Medium	Growing	Medium	Small	Small	Small
Stack Overflow Tags	Active	Growing	Growing	Active	Limited	Limited	Growing

Choosing the Right Solution

Choose Keycloak If:

• You need SAML support for enterprise customers
• You need LDAP/Active Directory federation
• You have Java expertise on your team
• You need the most mature and battle-tested option
• You want the largest community and extension ecosystem
• You need fine-grained authorization with UMA

Choose Authentik If:

• You need a reverse proxy authentication mode (forward auth)
• You want a visual flow designer
• You need LDAP compatibility (outpost)
• Your team prefers Python

Choose Zitadel If:

• You are building a multi-tenant B2B SaaS application
• You want low resource usage and simple deployment
• You prefer an event-sourced architecture
• You want built-in organizations without extensions

Choose Ory If:

• You want complete control over the user-facing UI
• You need OIDC certification
• You want a microservices-based identity layer
• You need Google Zanzibar-style authorization (Keto)

Choose Logto If:

• You want the best developer experience
• You are building a consumer-facing application
• Your team is TypeScript-native
• You want drop-in pre-built UI components

Cost of Self-Hosting vs Managed

All solutions listed are free to run yourself, but self-hosting has real costs: infrastructure, monitoring, security patching, upgrades, and on-call coverage. For a detailed cost analysis, see our post on the cost of self-hosting Keycloak.

For teams evaluating the ROI of managed vs self-hosted identity, the IAM ROI Calculator helps quantify the total cost of ownership.

Conclusion

Keycloak remains the most feature-complete and widely deployed open-source IAM solution, particularly for organizations that need SAML, LDAP federation, or deep customization. However, newer solutions like Zitadel and Authentik are credible alternatives for teams with different requirements or technology preferences.

If you have decided on Keycloak and want to get started quickly, check out our getting started guide. For production deployments without the operational burden, Skycloak’s managed hosting lets you focus on your application while we handle the infrastructure. Visit our pricing page to find the right plan.