Best Open Source Alternatives to Auth0 in 2026

Auth0 charges $23-240/month and gets expensive fast once you need features like SSO, MFA, or custom domains. Authentication is critical infrastructure — and open source options have reached production-ready maturity. Here's what works.

TL;DR

Keycloak is the enterprise standard — battle-tested, feature-complete, handles SSO/SAML/LDAP for large organizations. Authentik is the modern alternative — better UX, easier setup, built for cloud-native teams. Logto offers the best developer experience for startups and smaller apps. SuperTokens is ideal for developers who want auth libraries, not a platform.

Key Takeaways

Keycloak is the safe choice for enterprise — 20K+ GitHub stars, Red Hat backing, used by governments and Fortune 500s
Authentik has the best admin UX of any open source auth platform — modern, clean, fast
Logto is closest to Auth0's DX — management console, pre-built UI components, SDKs for every framework
SuperTokens gives you auth as a library, not a service — maximum control, embeds into your app
Zitadel is the new contender for multi-tenant SaaS — built-in organizations, machine-to-machine auth, event-sourced
Cost savings are enormous — Auth0 Professional at scale costs $5K-20K+/year; self-hosting costs $200-500/year

The Comparison

Feature	Auth0	Keycloak	Authentik	Logto	SuperTokens	Zitadel
Price	$23-240/mo	Free	Free	Free	Free	Free
SSO/SAML	✅	✅ (best)	✅	✅	❌	✅
OIDC/OAuth 2.0	✅	✅	✅	✅	✅	✅
Social login	✅	✅	✅	✅	✅	✅
MFA/2FA	✅	✅	✅	✅	✅	✅
Passwordless	✅	✅	✅	✅	✅	✅
Passkeys	✅	✅	✅	✅	❌	✅
LDAP	✅	✅	✅	❌	❌	✅
User management	✅	✅	✅	✅	✅	✅
Pre-built UI	✅	✅	✅	✅	✅	✅
Custom branding	✅	✅	✅	✅	✅	✅
Organizations	✅	Realms	Tenants	Orgs	❌	✅ (best)
Admin console	✅	✅	✅ (best)	✅	Dashboard	✅
Setup time	Minutes	Hours	30 min	15 min	30 min	30 min

1. Keycloak

The enterprise identity standard.

GitHub: 24K+ stars
Stack: Java (Quarkus), PostgreSQL
License: Apache 2.0
Deploy: Docker, Kubernetes (Operator), standalone

Keycloak is the go-to for enterprise authentication. It handles everything — SAML 2.0, OIDC, LDAP federation, Kerberos, social login, MFA, fine-grained authorization, user federation from Active Directory, and more. Red Hat maintains it (as the upstream for Red Hat SSO).

Standout features:

Complete SAML and OIDC implementation
LDAP/Active Directory federation
Fine-grained authorization services
Identity brokering (federate with other IdPs)
Realms for multi-tenant isolation
Admin console with full user/role/permission management
Client adapters for Java, JavaScript, Node.js, Python
Custom authentication flows (drag-and-drop flow builder)
Account management console for end users

Deploy:

docker run -p 8080:8080 \
  -e KC_BOOTSTRAP_ADMIN_USERNAME=admin \
  -e KC_BOOTSTRAP_ADMIN_PASSWORD=admin \
  quay.io/keycloak/keycloak:latest start-dev

Best for: Enterprises needing SAML/LDAP, organizations with Active Directory, government/regulated industries, large-scale multi-tenant deployments.

Trade-off: Java-based, so resource-hungry (2-4 GB RAM minimum). Admin console is functional but dated compared to newer alternatives.

2. Authentik

Modern identity management with the best admin UX.

GitHub: 14K+ stars
Stack: Python (Django), Go (outpost proxy), PostgreSQL
License: MIT (source available)
Deploy: Docker, Kubernetes

Authentik is what Keycloak would look like if redesigned in 2024. The admin console is beautiful and intuitive. Setup is faster. It supports the same enterprise protocols (SAML, OIDC, LDAP, SCIM) but with a more modern architecture.

Standout features:

Beautiful, modern admin interface
Flow-based authentication (visual flow builder)
LDAP outpost (Authentik as an LDAP server)
SAML, OIDC, proxy authentication
Application-level access control
Blueprints for reproducible configurations
Built-in outpost proxy for legacy apps
Event logging and audit trail
Multi-tenancy

Best for: Teams that want enterprise auth features with modern UX, cloud-native organizations, anyone frustrated with Keycloak's admin console.

3. Logto

The developer-friendly auth platform.

GitHub: 9K+ stars
Stack: TypeScript, Node.js, PostgreSQL
License: MPL-2.0
Deploy: Docker, npm

Logto is closest to Auth0's developer experience. It has a polished management console, pre-built sign-in UI (customizable), SDKs for every major framework, and a clean API. If you're a startup or small team that values DX above all else, Logto is the choice.

Standout features:

Pre-built sign-in experience (customizable, multi-language)
SDKs for Next.js, React, Vue, Express, Go, Python, etc.
Management console with user analytics
Social connectors (Google, GitHub, Apple, etc.)
Machine-to-machine authentication
Organizations for multi-tenant SaaS
Webhooks for event-driven integrations
Audit logs
Custom JWT claims

Best for: Startups, SaaS products, developers wanting the fastest path to production auth, teams coming from Auth0.

4. SuperTokens

Auth as a library, not a service.

GitHub: 13K+ stars
Stack: Java (core), Node.js/Python/Go SDKs
License: Apache 2.0
Deploy: Docker, managed cloud

SuperTokens takes a different approach — instead of a standalone identity server, it's a library that embeds into your app. You get pre-built auth recipes (email/password, social, passwordless, MFA) that run in your backend, giving you maximum control over the auth flow.

Standout features:

Recipe-based architecture (mix and match auth methods)
Pre-built UI components (React, vanilla JS)
Backend SDKs for Node.js, Python, Go
Session management with anti-CSRF
User roles and permissions
Multi-tenancy support
Override system for customizing any behavior
Dashboard for user management

Best for: Developers who want maximum control, teams building custom auth flows, apps where auth must be deeply integrated into the backend.

5. Zitadel

Built for multi-tenant SaaS.

GitHub: 10K+ stars
Stack: Go, CockroachDB/PostgreSQL
License: Apache 2.0
Deploy: Docker, Kubernetes, binary

Zitadel is purpose-built for multi-tenant SaaS applications. Organizations (tenants) are first-class — each can have its own branding, policies, IdP connections, and user base. The event-sourced architecture provides a complete audit trail.

Standout features:

Multi-tenant organizations as a core concept
Machine-to-machine auth with service users
Event-sourced architecture (complete audit trail)
Actions system (like Auth0 Actions — custom logic on auth events)
Built-in user management UI
Personal access tokens
Fine-grained role-based access
Branding per organization

Best for: B2B SaaS needing per-customer auth configuration, applications with machine-to-machine communication, teams wanting an event-sourced identity layer.

Cost Comparison

Scenario	Auth0	Keycloak	Logto	SuperTokens
1K MAU	$23/month	$10/month (VPS)	$5/month	$5/month
10K MAU	$228/month	$20/month	$10/month	$10/month
50K MAU	$800+/month	$40/month	$20/month	$20/month
Enterprise + SSO	$1,500+/month	$50/month	$30/month	N/A

Decision Guide

Choose Keycloak if:

Enterprise is the primary use case (SAML, LDAP, AD federation)
You're in a regulated industry
You need the most battle-tested, widely deployed option
Java ecosystem is familiar to your team

Choose Authentik if:

You want enterprise features with modern UX
Admin console quality matters
You need LDAP outpost or proxy authentication
You value visual flow-based configuration

Choose Logto if:

Developer experience is the top priority
You're building a SaaS product
You want the fastest setup with pre-built UI
You're coming from Auth0 and want a similar experience

Choose SuperTokens if:

You want auth as a library, not a separate server
You need maximum control over the auth flow
You're building custom auth experiences
Apache 2.0 licensing is important

Choose Zitadel if:

You're building B2B SaaS with per-customer auth
Multi-tenancy is a core requirement
You need machine-to-machine auth
Event sourcing and complete audit trails matter

Choosing the Right Auth0 Alternative

The decision between Keycloak, Authentik, Logto, and Zitadel comes down to four key variables: team size, enterprise SSO requirements, developer experience priorities, and long-term maintenance appetite. Getting this choice right upfront matters — migrating identity platforms is painful, and you want to pick the right tool the first time.

Team Size and Organizational Complexity

Small teams and startups (1-20 engineers) should default to either Logto or Authentik. Logto's guided setup, pre-built sign-in UI, and SDKs for every major framework get you from zero to production auth in under an hour. If you're used to Auth0's management console, Logto will feel immediately familiar. Authentik is a good alternative if you anticipate needing SAML federation or proxy auth for internal tools down the road — features Logto doesn't cover yet.

Mid-size engineering organizations (20-200 engineers) are often best served by Authentik. The visual flow builder handles complex multi-step authentication logic without writing code. LDAP outpost support means you can expose Authentik as an LDAP server for legacy tools. The admin UX is genuinely excellent — teams that lose hours to Keycloak's dated console consistently report faster admin work in Authentik.

Enterprise teams (200+ engineers, multiple departments) should look seriously at Keycloak. It's the only option on this list with 20+ years of production deployments in regulated industries, government environments, and Fortune 500 companies. The Red Hat backing means long-term support is guaranteed. If your organization uses Active Directory and needs LDAP federation, Keycloak handles it more completely than any alternative.

Enterprise SSO Requirements

SSO via SAML 2.0 is a hard requirement for selling B2B software — enterprise customers won't sign without it. All five tools support SAML, but there are meaningful differences in implementation depth.

Keycloak has the most mature SAML implementation, used in integrations with hundreds of enterprise IdPs. If you're connecting to Okta, Azure AD, or a government SAML provider, Keycloak's compatibility track record is unmatched.

Authentik and Zitadel both offer solid SAML support. Zitadel adds per-organization SAML configuration, which is essential for B2B SaaS products where each enterprise customer brings their own IdP. For a comparison of how these platforms handle enterprise identity federation, see Authentik vs Keycloak vs Authelia: enterprise auth comparison.

Developer Experience

Developer experience (DX) determines how quickly your team ships auth features and how much time goes into debugging. Logto leads DX by a wide margin — the management API, SDKs, and documentation are clearly written by developers who have used Auth0 and set out to improve it. For startups moving fast, this matters. For a focused DX comparison between two modern auth platforms, see Authentik vs Logto: which modern auth platform fits your stack?.

Keycloak has the worst DX of the group — extensive Java configuration, XML-based client adapters for older frameworks, and a steep learning curve. It's powerful but verbose.

Migrating from Auth0

The most common migration path in 2026 is Auth0 to Keycloak for enterprise teams, and Auth0 to Logto for startups. Both involve exporting users (hashed passwords), configuring OIDC clients in the new platform, and updating your application's auth SDK. For a detailed migration playbook covering user export, credential migration, and application reconfiguration, see our guide to migrating from Auth0 to Keycloak.

The short version: Logto's Auth0 migration guide in their documentation is the most beginner-friendly. Keycloak's migration is more manual but better documented for complex SAML and LDAP scenarios.

Compare open source authentication platforms on OSSAlt — features, protocol support, deployment options, and community health side by side.

See open source alternatives to Auth0 on OSSAlt.

The SaaS-to-Self-Hosted Migration Guide (Free PDF)