Open Source Alternatives to Auth0 2026

TL;DR

Auth0 costs $23+/month for 1,000 monthly active users and gets expensive fast. Three compelling open source alternatives in 2026: Keycloak (Apache 2.0, ~23K stars, Java) is the battle-tested enterprise identity platform — powerful but complex. Zitadel (Apache 2.0, ~8K stars, Go) is the modern cloud-native identity server with excellent developer experience. Logto (MPL 2.0, ~9K stars, TypeScript) is the newest contender — beautiful UI, fast setup, developer-focused. Also note Authentik (covered separately) as another strong option.

Key Takeaways

• Keycloak: Most battle-tested, enormous feature set, complex admin UI, high RAM (~512MB–1GB)
• Zitadel: Modern Go service, excellent API, multi-tenancy, ~100MB RAM
• Logto: Best onboarding experience, TypeScript, modern UI, good for startups and SaaS
• All support: OAuth2, OIDC, SAML 2.0, MFA (TOTP + WebAuthn/Passkeys), social login
• Auth0 pricing trap: $23/month at 1K MAU → $240/month at 7K MAU → $800+/month at 50K MAU
• Self-hosted cost: $5–20/month VPS regardless of user count

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Feature Comparison

Feature	Keycloak	Zitadel	Logto	Auth0
License	Apache 2.0	Apache 2.0	MPL 2.0	Proprietary
GitHub Stars	~23K	~8K	~9K	—
Language	Java	Go	TypeScript	—
OAuth2/OIDC	Yes	Yes	Yes	Yes
SAML 2.0	Yes	Yes	No	Yes
MFA (TOTP)	Yes	Yes	Yes	Yes
Passkeys	Yes	Yes	Yes	Yes
Social login	Yes	Yes	Yes	Yes
LDAP/AD	Yes	Yes	No	Yes
Multi-tenancy	Organizations	Yes (native)	Yes	Yes
Machine-to-machine	Yes	Yes	Yes	Yes
Admin UI	Complex	Good	Excellent	Excellent
RAM (idle)	~512MB–1GB	~100MB	~200MB	—
Price (cloud)	Free	Free (cloud free tier)	Free (cloud free tier)	$23+/mo (1K MAU)

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Option 1: Keycloak — Enterprise Battle-Tested

Keycloak is the most mature and feature-rich option. Used by Red Hat, banks, governments, and enterprises worldwide.

Docker Setup

services:
  keycloak-db:
    image: postgres:16-alpine
    restart: unless-stopped
    environment:
      POSTGRES_DB: keycloak
      POSTGRES_USER: keycloak
      POSTGRES_PASSWORD: "${POSTGRES_PASSWORD}"
    volumes:
      - keycloak_db:/var/lib/postgresql/data

  keycloak:
    image: quay.io/keycloak/keycloak:latest
    container_name: keycloak
    restart: unless-stopped
    ports:
      - "8080:8080"
    command: start
    environment:
      KC_DB: postgres
      KC_DB_URL: jdbc:postgresql://keycloak-db:5432/keycloak
      KC_DB_USERNAME: keycloak
      KC_DB_PASSWORD: "${POSTGRES_PASSWORD}"
      KC_HOSTNAME: "auth.yourdomain.com"
      KC_PROXY: "edge"    # Behind reverse proxy
      KEYCLOAK_ADMIN: admin
      KEYCLOAK_ADMIN_PASSWORD: "${ADMIN_PASSWORD}"
    depends_on:
      - keycloak-db

auth.yourdomain.com {
    reverse_proxy localhost:8080
}

Keycloak Concepts

• Realm: An isolated tenant (create one per environment: dev, prod)
• Client: An application that uses Keycloak for auth
• User: A person who can log in
• Role: Permission assigned to users or groups
• Identity Provider: External login (GitHub, Google, LDAP)

Configure a Client (OIDC)

1. Admin Console → Your Realm → Clients → Create Client
2. Client type: OpenID Connect
3. Client ID: myapp
4. Valid redirect URIs: https://myapp.yourdomain.com/*
5. Copy Client Secret from Credentials tab

In your app:

OIDC_ISSUER=https://auth.yourdomain.com/realms/myrealm
OIDC_CLIENT_ID=myapp
OIDC_CLIENT_SECRET=your-client-secret

---

Option 2: Zitadel — Modern Cloud-Native

Zitadel is built in Go, cloud-native from the ground up, with excellent multi-tenancy and a developer-friendly API.

Docker Setup

services:
  zitadel:
    restart: always
    image: ghcr.io/zitadel/zitadel:stable
    command: start-from-init --masterkey "${ZITADEL_MASTERKEY}" --tlsMode disabled
    environment:
      ZITADEL_DATABASE_POSTGRES_HOST: db
      ZITADEL_DATABASE_POSTGRES_PORT: "5432"
      ZITADEL_DATABASE_POSTGRES_DATABASE: zitadel
      ZITADEL_DATABASE_POSTGRES_USER_USERNAME: zitadel
      ZITADEL_DATABASE_POSTGRES_USER_PASSWORD: "${POSTGRES_PASSWORD}"
      ZITADEL_DATABASE_POSTGRES_ADMIN_USERNAME: postgres
      ZITADEL_DATABASE_POSTGRES_ADMIN_PASSWORD: "${POSTGRES_PASSWORD}"
      ZITADEL_EXTERNALDOMAIN: "auth.yourdomain.com"
      ZITADEL_EXTERNALPORT: "443"
      ZITADEL_EXTERNALSECURE: "true"
    ports:
      - "8080:8080"
    depends_on:
      db:
        condition: service_healthy

  db:
    restart: always
    image: postgres:16-alpine
    environment:
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: "${POSTGRES_PASSWORD}"
    volumes:
      - zitadel_db:/var/lib/postgresql/data
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U postgres"]
      interval: 10s

# Generate masterkey:
openssl rand -base64 32

docker compose up -d

Create an Application in Zitadel

1. Login with initial admin credentials (shown in startup logs)
2. Console → Projects → Create New Project
3. Applications → New Application → Web
4. Authentication Method: PKCE (for frontend) or CODE (for backend)
5. Redirect URIs: https://myapp.yourdomain.com/auth/callback
6. Copy Client ID

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Option 3: Logto — Best Developer Experience

Logto (MPL 2.0, ~9K stars, TypeScript) has the best onboarding and admin UI. Great for SaaS builders.

Docker Setup

services:
  logto:
    image: svhd/logto:latest
    container_name: logto
    ports:
      - "3001:3001"    # Management API + Admin
      - "3000:3000"    # OIDC endpoint
    environment:
      DB_URL: postgresql://logto:${POSTGRES_PASSWORD}@db:5432/logto
      ENDPOINT: "https://auth.yourdomain.com"
      ADMIN_ENDPOINT: "https://logto-admin.yourdomain.com"
    depends_on:
      db:
        condition: service_healthy
    entrypoint: ["sh", "-c", "npm run cli db seed -- --swe && npm start"]

  db:
    image: postgres:16-alpine
    environment:
      POSTGRES_DB: logto
      POSTGRES_USER: logto
      POSTGRES_PASSWORD: "${POSTGRES_PASSWORD}"
    volumes:
      - logto_db:/var/lib/postgresql/data
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U logto"]
      interval: 10s

auth.yourdomain.com {
    reverse_proxy localhost:3000
}

logto-admin.yourdomain.com {
    reverse_proxy localhost:3001
}

Add Social Login (GitHub example)

1. Admin Console → Connectors → Social → GitHub
2. Enter GitHub OAuth App Client ID + Secret
3. Enable "Sign in with GitHub" button on login page

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Which to Choose

Choose Keycloak if:

• Enterprise with SAML requirements (Salesforce, Azure AD, enterprise SSO)
• LDAP/Active Directory integration needed
• Large team with complex role/permission hierarchies
• You have Java expertise for customization

Choose Zitadel if:

• Multi-tenant SaaS product where each customer is an "organization"
• You want machine-to-machine (M2M) auth with a clean API
• Modern Go stack, low RAM footprint
• Event-driven architecture (Zitadel uses event sourcing internally)

Choose Logto if:

• Developer-focused product with a polished login UI
• You want the fastest time-to-working-auth
• TypeScript ecosystem (Logto SDKs are excellent)
• Building a consumer or B2B SaaS where UX of the login page matters

See also: Auth.js v5 vs Lucia v3 vs Better Auth on StarterPick — reviewed open-source auth libraries for SaaS starters.

---

See all open source authentication and identity tools at OSSAlt.com/categories/authentication.

See open source alternatives to Auth0 on OSSAlt.

Authentication and Access Control

Self-hosted services should not be exposed to the internet without authentication. Even services with built-in user accounts benefit from an additional authentication layer that prevents credential stuffing and brute force attacks.

Reverse proxy authentication with Authelia adds two-factor authentication and single sign-on to any Docker service without modifying the application. Authelia sits in front of your Nginx or Traefik reverse proxy and enforces authentication before the request reaches your application. It supports TOTP, WebAuthn, and push notifications.

Identity provider (SSO) with Authentik takes this further — instead of per-application accounts, users authenticate once through Authentik and access all your self-hosted services. Authentik supports SAML, OIDC, and LDAP, making it compatible with services that have enterprise authentication built in.

Password management: If you're managing multiple self-hosted services with different credentials, Vaultwarden provides a fully featured Bitwarden-compatible server on a $5/month VPS. Browser extensions and mobile apps give your team secure shared access to service credentials without LastPass or 1Password subscriptions.

Network isolation: Use Docker networks to prevent containers from communicating directly when they shouldn't. Services that don't need public internet exposure should only have internal networking. Traefik's middleware system lets you add IP allowlisting, rate limiting, and basic auth at the ingress layer without touching application configuration.

Network Security and Hardening

Self-hosted services exposed to the internet require baseline hardening. The default Docker networking model exposes container ports directly — without additional configuration, any open port is accessible from anywhere.

Firewall configuration: Use ufw (Uncomplicated Firewall) on Ubuntu/Debian or firewalld on RHEL-based systems. Allow only ports 22 (SSH), 80 (HTTP redirect), and 443 (HTTPS). Block all other inbound ports. Docker bypasses ufw's OUTPUT rules by default — install the ufw-docker package or configure Docker's iptables integration to prevent containers from opening ports that bypass your firewall rules.

SSH hardening: Disable password authentication and root login in /etc/ssh/sshd_config. Use key-based authentication only. Consider changing the default SSH port (22) to a non-standard port to reduce brute-force noise in your logs.

Fail2ban: Install fail2ban to automatically ban IPs that make repeated failed authentication attempts. Configure jails for SSH, Nginx, and any application-level authentication endpoints.

TLS/SSL: Use Let's Encrypt certificates via Certbot or Traefik's automatic ACME integration. Never expose services over HTTP in production. Configure HSTS headers to prevent protocol downgrade attacks. Check your SSL configuration with SSL Labs' server test — aim for an A or A+ rating.

Container isolation: Avoid running containers as root. Add user: "1000:1000" to your docker-compose.yml service definitions where the application supports non-root execution. Use read-only volumes (volumes: - /host/path:/container/path:ro) for configuration files the container only needs to read.

Secrets management: Never put passwords and API keys directly in docker-compose.yml files committed to version control. Use Docker secrets, environment files (.env), or a secrets manager like Vault for sensitive configuration. Add .env to your .gitignore before your first commit.

Production Deployment Checklist

Before treating any self-hosted service as production-ready, work through this checklist. Each item represents a class of failure that will eventually affect your service if left unaddressed.

Infrastructure

• Server OS is running latest security patches (apt upgrade / dnf upgrade)
• Firewall configured: only ports 22, 80, 443 open
• SSH key-only authentication (password auth disabled)
• Docker and Docker Compose are current stable versions
• Swap space configured (at minimum equal to RAM for <4GB servers)

Application

• Docker image version pinned (not latest) in docker-compose.yml
• Data directories backed by named volumes (not bind mounts to ephemeral paths)
• Environment variables stored in .env file (not hardcoded in compose)
• Container restart policy set to unless-stopped or always
• Health check configured in Compose or Dockerfile

Networking

• SSL certificate issued and auto-renewal configured
• HTTP requests redirect to HTTPS
• Domain points to server IP (verify with dig +short your.domain)
• Reverse proxy (Nginx/Traefik) handles SSL termination

Monitoring and Backup

• Uptime monitoring configured with alerting
• Automated daily backup of Docker volumes to remote storage
• Backup tested with a successful restore drill
• Log retention configured (no unbounded log accumulation)

Access Control

• Default admin credentials changed
• Email confirmation configured if the app supports it
• User registration disabled if the service is private
• Authentication middleware added if the service lacks native login

Conclusion

The decision to self-host is ultimately a question of constraints and priorities. Data ownership, cost control, and customization are legitimate reasons to run your own infrastructure. Operational complexity, reliability guarantees, and time cost are legitimate reasons not to.

The practical path forward is incremental. Start with the service where self-hosting provides the most clear value — usually the one with the highest SaaS cost or the most sensitive data. Build your operational foundation (monitoring, backup, SSL) correctly for that first service, then evaluate whether to expand.

Self-hosting done well is not significantly more complex than using SaaS. The tools available in 2026 — containerization, automated certificate management, hosted monitoring services, and S3-compatible backup storage — have reduced the operational overhead to something manageable for any developer comfortable with the command line. What it requires is discipline: consistent updates, tested backups, and monitoring that alerts before users do.

The self-hosted identity provider landscape has matured significantly. Authentik and Authelia are both production-ready, well-documented, and actively maintained. The choice between them comes down to scope: Authelia is a focused authentication proxy that adds 2FA in front of existing applications, while Authentik is a full identity provider with user management, SAML/OIDC/LDAP support, and workflow automation. For most self-hosting setups, start with Authelia for simplicity and migrate to Authentik if you need SSO across multiple applications with centralized user management.

Self-hosted authentication middleware earns its operational overhead by eliminating per-authentication-event API call costs and ensuring your auth stack works even when cloud providers have incidents. Configure health monitoring for your auth service — Uptime Kuma can check your Authelia or Authentik health endpoint every 30 seconds and alert if it becomes unavailable. An authentication outage is one of the most impactful failures in any web application stack, so monitoring it as carefully as your primary application service is not optional.