Commercial identity providers (Okta, Auth0, Azure AD B2C) cost $3–$8 per monthly active user. For a 10,000 MAU app, that's $30,000–$80,000/year. Self-hosted alternatives reduce that to server costs ($50–$200/month). Beyond cost, self-hosted IAM means: Data sovereignty — user credentials stay in your infrastructure No vendor lock-in — migrate freely between identity providers Custom flows — registration, login, and MFA flows you fully control Compliance — healthcare, finance, and government requi

Choose Zitadel if: You're building a SaaS product with multi-tenant organization management (B2B auth) Kubernetes-native deployment with Go's operational characteristics matter You want the cleanest OIDC implementation with the smallest config surface Your auth flows are standard (login, registration, MFA) without exotic customization Choose Casdoor if: Your authorization requirements are complex (RBAC + ABAC + domain-level policies) You already use or want Casbin's policy model You need unified

Zitadel vs Casdoor vs Authentik: Open Source IAM in 2026

TL;DR

Zitadel is the cloud-native identity server built in Go — designed for SaaS multi-tenancy, B2B scenarios, and Kubernetes-first deployments. Clean admin UI, excellent OIDC implementation, and strong organization (tenant) management. Casdoor is the access control specialist — built on Casbin, it handles complex permission models (RBAC, ABAC, ACL) alongside standard authentication. Best when your use case involves fine-grained authorization, not just authentication. Authentik is the most flexible all-rounder — Python/Go hybrid, works as SSO provider, identity proxy, or LDAP provider, with the richest integration ecosystem. For SaaS B2B multi-tenancy: Zitadel. For complex authorization rules: Casdoor. For replacing enterprise tools (Okta/Auth0 self-hosted): Authentik.

Key Takeaways

Zitadel GitHub stars: ~9k — the fastest-growing modern identity server
Authentik has 200+ integrations — LDAP, RADIUS, SAML, OIDC, proxy mode covers most enterprise apps
Casdoor uses Casbin's policy engine — supports RBAC, ABAC, ACL, RESTful, and URL-matching models
All three support OIDC, OAuth 2.0, and SAML 2.0 — standard protocol coverage is solid
Zitadel requires the least configuration for a clean OIDC/OAuth setup
Authentik's proxy mode can add SSO to apps that don't support it natively (Nginx auth_request)
All three ship as Docker containers — deployable in <30 minutes for basic setup

Why Self-Hosted IAM?

Commercial identity providers (Okta, Auth0, Azure AD B2C) cost $3–$8 per monthly active user. For a 10,000 MAU app, that's $30,000–$80,000/year. Self-hosted alternatives reduce that to server costs ($50–$200/month).

Beyond cost, self-hosted IAM means:

Data sovereignty — user credentials stay in your infrastructure
No vendor lock-in — migrate freely between identity providers
Custom flows — registration, login, and MFA flows you fully control
Compliance — healthcare, finance, and government require specific data residency

Zitadel: Cloud-Native Identity for SaaS

Zitadel is built for multi-tenant SaaS from the ground up. Every concept (organization, project, application, user) maps to the multi-tenant model. Written in Go, it runs as a single binary backed by CockroachDB or PostgreSQL.

Docker Compose Setup

version: "3.8"

services:
  db:
    image: postgres:16-alpine
    environment:
      POSTGRES_DB: zitadel
      POSTGRES_USER: zitadel
      POSTGRES_PASSWORD: zitadel-db-password
    volumes:
      - zitadel-db:/var/lib/postgresql/data

  zitadel:
    image: ghcr.io/zitadel/zitadel:latest
    command: start-from-init --masterkey "MasterkeyNeedsToHave32Characters" --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: zitadel-db-password
      ZITADEL_DATABASE_POSTGRES_USER_SSL_MODE: disable
      ZITADEL_EXTERNALDOMAIN: localhost
      ZITADEL_EXTERNALPORT: 8080
    ports:
      - "8080:8080"
    depends_on:
      - db

volumes:
  zitadel-db:

OIDC Integration (Node.js)

// Zitadel OIDC with openid-client
import { Issuer, generators } from "openid-client";

async function setupZitadelOIDC() {
  const issuer = await Issuer.discover("https://your-zitadel.com");

  const client = new issuer.Client({
    client_id: process.env.ZITADEL_CLIENT_ID!,
    client_secret: process.env.ZITADEL_CLIENT_SECRET!,
    redirect_uris: ["https://yourapp.com/callback"],
    response_types: ["code"],
  });

  return client;
}

// Authorization URL
const codeVerifier = generators.codeVerifier();
const codeChallenge = generators.codeChallenge(codeVerifier);

const authUrl = client.authorizationUrl({
  scope: "openid email profile",
  code_challenge: codeChallenge,
  code_challenge_method: "S256",
});

// Token exchange after callback
const tokenSet = await client.callback(
  "https://yourapp.com/callback",
  { code: callbackCode },
  { code_verifier: codeVerifier }
);

const userinfo = await client.userinfo(tokenSet.access_token!);

Zitadel Management API (Multi-Tenancy)

// Create a new organization (tenant) programmatically
async function createOrganization(name: string, adminEmail: string) {
  const response = await fetch(
    "https://your-zitadel.com/management/v1/orgs",
    {
      method: "POST",
      headers: {
        Authorization: `Bearer ${serviceAccountToken}`,
        "Content-Type": "application/json",
      },
      body: JSON.stringify({ name }),
    }
  );

  const org = await response.json();
  return org.org.id;
}

// Invite a user to an organization
async function inviteUser(orgId: string, email: string) {
  await fetch(
    `https://your-zitadel.com/management/v1/orgs/${orgId}/members`,
    {
      method: "POST",
      headers: {
        Authorization: `Bearer ${serviceAccountToken}`,
        "Content-Type": "application/json",
        "x-zitadel-orgid": orgId,
      },
      body: JSON.stringify({
        userId: email,
        roles: ["ORG_OWNER"],
      }),
    }
  );
}

Zitadel Actions (Custom Logic)

// Zitadel Actions — JavaScript functions that run during auth flows
// Add this via the Admin Console under "Actions"

// Example: Add custom claims to tokens
function setCustomClaims(ctx, api) {
  // ctx contains user info, request details
  const orgId = ctx.org.id;

  // Add org tier from your database (simulated here)
  const tier = lookupTier(orgId); // Your custom function

  api.v1.claims.setClaim("org_tier", tier);
  api.v1.claims.setClaim("org_id", orgId);
}

Casdoor: Access Control Meets Identity

Casdoor combines authentication with Casbin's powerful policy engine. While most identity servers do authentication and basic role-based access control, Casdoor handles complex permission models natively.

Docker Compose Setup

version: "3.8"

services:
  db:
    image: mysql:8-debian
    environment:
      MYSQL_ROOT_PASSWORD: casdoor-root
      MYSQL_DATABASE: casdoor
    volumes:
      - casdoor-db:/var/lib/mysql

  casdoor:
    image: casbin/casdoor-all-in-one:latest
    ports:
      - "8000:8000"
    environment:
      RUNNING_IN_DOCKER: "true"
    depends_on:
      - db

volumes:
  casdoor-db:

OIDC Integration

// Casdoor is OIDC-compliant — standard integration
import { casdoor } from "casdoor-nodejs-sdk";

const casdoorConfig = {
  endpoint: "http://localhost:8000",
  clientId: process.env.CASDOOR_CLIENT_ID!,
  clientSecret: process.env.CASDOOR_CLIENT_SECRET!,
  certificate: process.env.CASDOOR_PUBLIC_CERT!,
  orgName: "my-organization",
  appName: "my-app",
};

const sdk = new casdoor.SDK(casdoorConfig);

// Get authorization URL
const authUrl = sdk.getAuthLink(
  "https://yourapp.com/callback",
  "state-random-string",
  "code",
  "openid email profile"
);

// Exchange code for token
const token = await sdk.getOAuthToken(
  "code-from-callback",
  "https://yourapp.com/callback"
);

const userInfo = await sdk.parseJwtToken(token.access_token);

Casbin Permission Policies

// Casdoor uses Casbin's policy engine — define complex authorization rules

// RBAC policy (model.conf)
// [request_definition]
// r = sub, obj, act
// [policy_definition]
// p = sub, obj, act
// [role_definition]
// g = _, _
// [matchers]
// m = g(r.sub, p.sub) && r.obj == p.obj && r.act == p.act

// Policies (stored in Casdoor database, manageable via UI):
// p, admin, /api/*, *          # Admins can do anything on /api/*
// p, user, /api/read/*, GET   # Users can GET from /api/read/*
// g, alice, admin              # alice is an admin
// g, bob, user                 # bob is a user

// Policy enforcement in your app
import { Enforcer } from "casbin";
import { CasdoorAdapter } from "casbin-casdoor-adapter";

const enforcer = await Enforcer.newEnforcer(
  "path/to/model.conf",
  new CasdoorAdapter(casdoorConfig)
);

// Check permission
async function canAccess(userId: string, resource: string, action: string) {
  const allowed = await enforcer.enforce(userId, resource, action);
  return allowed;
}

// Usage
if (await canAccess("alice", "/api/users/123", "DELETE")) {
  // Proceed with deletion
}

ABAC (Attribute-Based Access Control)

// Casdoor ABAC — policy based on attributes, not just roles

// Model: r = sub_attr, dom, obj_attr, act
// p = sub_attr.department == "engineering" && obj_attr.sensitivity == "low", *, *, read

const enforcer = await Enforcer.newEnforcer("abac-model.conf", "abac-policy.csv");

// Pass attribute objects directly
const user = { id: "user_123", department: "engineering", clearance: "level2" };
const document = { id: "doc_456", sensitivity: "low", owner: "user_789" };

const canRead = await enforcer.enforce(user, "company-portal", document, "read");
const canEdit = await enforcer.enforce(user, "company-portal", document, "write");

Authentik: The Enterprise-Grade All-Rounder

Authentik is written in Python (backend) and TypeScript (frontend) and provides the most comprehensive integration surface: OIDC provider, SAML provider, LDAP server, RADIUS server, and application proxy. It can SSO-enable any app, even ones without native SSO support.

Docker Compose Setup

version: "3.8"

services:
  postgresql:
    image: docker.io/library/postgres:16-alpine
    environment:
      POSTGRES_PASSWORD: authentik-db-pass
      POSTGRES_USER: authentik
      POSTGRES_DB: authentik
    volumes:
      - authentik-db:/var/lib/postgresql/data

  redis:
    image: docker.io/library/redis:alpine

  server:
    image: ghcr.io/goauthentik/server:latest
    command: server
    environment:
      AUTHENTIK_REDIS__HOST: redis
      AUTHENTIK_POSTGRESQL__HOST: postgresql
      AUTHENTIK_POSTGRESQL__USER: authentik
      AUTHENTIK_POSTGRESQL__NAME: authentik
      AUTHENTIK_POSTGRESQL__PASSWORD: authentik-db-pass
      AUTHENTIK_SECRET_KEY: "your-secret-key-min-50-chars-long"
      AUTHENTIK_ERROR_REPORTING__ENABLED: "false"
    ports:
      - "9000:9000"
      - "9443:9443"
    depends_on:
      - postgresql
      - redis

  worker:
    image: ghcr.io/goauthentik/server:latest
    command: worker
    environment:
      AUTHENTIK_REDIS__HOST: redis
      AUTHENTIK_POSTGRESQL__HOST: postgresql
      AUTHENTIK_POSTGRESQL__USER: authentik
      AUTHENTIK_POSTGRESQL__NAME: authentik
      AUTHENTIK_POSTGRESQL__PASSWORD: authentik-db-pass
      AUTHENTIK_SECRET_KEY: "your-secret-key-min-50-chars-long"
    depends_on:
      - postgresql
      - redis

volumes:
  authentik-db:

OIDC Provider Integration

// Authentik as OIDC provider
import { generators, Issuer } from "openid-client";

const issuer = await Issuer.discover("https://auth.yourcompany.com/application/o/your-app/");

const client = new issuer.Client({
  client_id: process.env.AUTHENTIK_CLIENT_ID!,
  client_secret: process.env.AUTHENTIK_CLIENT_SECRET!,
  redirect_uris: ["https://yourapp.com/callback"],
  response_types: ["code"],
});

Authentik Proxy Mode (SSO for Legacy Apps)

# nginx.conf — Authentik outpost proxy mode
# Adds SSO to any app without changing the app itself

upstream authentik {
  server authentik-outpost:9000;
}

server {
  listen 443 ssl;
  server_name legacy-app.company.com;

  location /outpost.goauthentik.io {
    proxy_pass http://authentik;
    proxy_set_header Host $host;
    proxy_set_header X-Original-URL $scheme://$host$request_uri;
    add_header Set-Cookie $auth_cookie;
    auth_request_set $auth_cookie $upstream_http_set_cookie;
  }

  # All requests go through auth check
  auth_request /outpost.goauthentik.io/auth/nginx;
  error_page 401 = @goauthentik_proxy_signin;
  auth_request_set $auth_header $upstream_http_authorization;
  proxy_set_header Authorization $auth_header;

  location @goauthentik_proxy_signin {
    internal;
    add_header Set-Cookie $auth_cookie;
    return 302 /outpost.goauthentik.io/start?rd=$request_uri;
  }

  location / {
    proxy_pass http://legacy-app-backend;
  }
}

Flows and Stages (Custom Auth Flows)

# Authentik policy — Python expressions for custom logic (in Admin UI)

# Example: Only allow users from specific email domains
def akpolicy_domain_check(request: PolicyRequest) -> PolicyResult:
    user = request.user
    allowed_domains = ["company.com", "partner.org"]
    email_domain = user.email.split("@")[-1]

    if email_domain in allowed_domains:
        return PolicyResult(passing=True)
    else:
        return PolicyResult(
            passing=False,
            messages=[f"Email domain {email_domain} is not allowed"]
        )

Feature Comparison

Feature	Zitadel	Casdoor	Authentik
Primary language	Go	Go	Python + Go
OIDC provider	✅	✅	✅
SAML 2.0	✅	✅	✅
LDAP server	Partial	✅	✅ Full
RADIUS server	❌	❌	✅
Proxy mode (SSO without code)	❌	❌	✅
Multi-tenancy / Organizations	✅ Native	✅	Partial
Fine-grained RBAC/ABAC	Basic roles	✅ Casbin	RBAC
Custom login flows	Actions (JS)	Partial	✅ Full flow engine
Social login (GitHub, Google)	✅	✅	✅ 30+ providers
User management UI	✅	✅	✅
Self-service password reset	✅	✅	✅
MFA (TOTP, WebAuthn)	✅	✅	✅
API-first management	✅ gRPC + REST	✅ REST	✅ REST
Kubernetes operator	✅	❌	❌
GitHub stars	9k	11k	16k
Docker image size	~50 MB	~150 MB	~500 MB
Memory usage (idle)	~100 MB	~100 MB	~300 MB

When to Use Each

Choose Zitadel if:

You're building a SaaS product with multi-tenant organization management (B2B auth)
Kubernetes-native deployment with Go's operational characteristics matter
You want the cleanest OIDC implementation with the smallest config surface
Your auth flows are standard (login, registration, MFA) without exotic customization

Choose Casdoor if:

Your authorization requirements are complex (RBAC + ABAC + domain-level policies)
You already use or want Casbin's policy model
You need unified auth + authorization in one system
Audit trails for who accessed what under which policy are required

Choose Authentik if:

You need to SSO-enable legacy apps without modifying them (proxy mode)
Your stack includes LDAP-dependent tools (GitLab, Jenkins, older enterprise apps)
You want the richest integration ecosystem (200+ provider support)
You're replacing Okta/Azure AD for a private company SSO layer

Ecosystem & Community

Authentik (16k GitHub stars) has the largest community of the three and the most comprehensive integration documentation. The Authentik community maintains integration guides for hundreds of applications, and the project has attracted enterprise contributions that have improved its reliability at scale. Authentik's Python backend has been partially rewritten in Go for performance-critical paths, addressing earlier concerns about Python's overhead for high-traffic auth systems.

Zitadel (9k GitHub stars) is backed by commercial support from the ZITADEL company, which provides hosted ZITADEL Cloud alongside the open-source version. The commercial backing has accelerated development — the team ships updates weekly and maintains comprehensive API documentation with code examples in Go, TypeScript, Java, Python, and C#. The Kubernetes operator makes Zitadel first-class in cloud-native environments.

Casdoor (11k GitHub stars) benefits from the broader Casbin ecosystem. Casbin's policy engine has millions of users across many languages, and Casdoor serves as the authentication layer on top of that proven authorization engine. The community around Casbin is particularly active in producing adapters for different databases and policy formats.

For teams choosing between these tools and commercial alternatives, the cost comparison is compelling. Authentik or Zitadel self-hosted on a $50/month VPS handles hundreds of thousands of users — the same workload on Auth0 would cost thousands per month.

Real-World Adoption

Authentik has become the standard recommendation in the self-hosted community (r/selfhosted, awesome-selfhosted) for teams replacing Okta or Azure AD in private infrastructure. Its proxy mode makes it uniquely useful for protecting internal tools — Grafana, Jupyter, internal documentation sites — without modifying those applications. The Nginx auth_request integration and Traefik forwardAuth integration are well-documented and widely deployed.

Zitadel sees strong adoption among B2B SaaS startups that need multi-tenant authentication from day one. The organization-centric data model maps directly to the SaaS concept of customer organizations, making it natural to provision separate authentication namespaces for each customer. Companies building HR tools, project management software, or any multi-tenant B2B product find that Zitadel's native organization support eliminates significant custom auth code.

Casdoor's adoption is concentrated in applications where authorization complexity is the primary concern. Healthcare applications with role-based access to patient records, financial systems with complex permission hierarchies, and multi-department enterprise tools all use Casdoor's Casbin integration to express policies that would be difficult to implement in simpler IAM systems.

The broader trend in 2026 is organizations moving from commercial identity providers to self-hosted alternatives driven by both cost and compliance requirements. The three tools collectively cover the major use cases, and the maturity of all three has reached a level where self-hosted IAM is a reasonable choice for most organizations.

Developer Experience Deep Dive

Zitadel's developer experience for OIDC integration is the cleanest of the three. The admin console is modern and well-organized, the OIDC discovery endpoint is standards-compliant, and the Node.js SDK examples are thorough. Setting up a new application in Zitadel — creating an OIDC application, configuring redirect URIs, getting the client ID and secret — takes about 10 minutes and the resulting integration works correctly with any OIDC client library.

Authentik's developer experience is more complex because of the concept of flows and stages. An authentication "flow" in Authentik is a configurable pipeline of stages (identification, password, MFA, etc.) that can be customized extensively. This power comes with a learning curve — understanding the flow/stage model takes time, but once understood it enables authentication experiences that no other self-hosted tool can match.

Casdoor's developer experience mirrors Casbin's, which is both a strength and a limitation. Teams already using Casbin for authorization will find Casdoor intuitive. Teams new to Casbin need to learn its model/policy abstraction before they can use Casdoor effectively. The documentation assumes Casbin familiarity, which creates a steeper onramp for teams coming from simpler IAM systems.

All three tools have comprehensive Docker Compose setup documentation, and all three can be running in a development environment in under 30 minutes following the official quick-start guides.

Security Considerations

All three tools implement standard OIDC and OAuth 2.0 correctly and support modern security practices: PKCE for public clients, token introspection, short-lived access tokens with refresh token rotation, and MFA including TOTP and WebAuthn. Security vulnerabilities are disclosed and patched promptly in all three projects.

Zitadel's security model benefits from its Go implementation and extensive security testing. The Zitadel team publishes security advisories and maintains a vulnerability disclosure process. The CockroachDB and PostgreSQL backend options both have strong security track records.

Authentik's Python backend has historically been the source of most security vulnerabilities, as Python web frameworks have a larger attack surface than Go. The Authentik team has improved their security posture significantly in recent releases, and the partial Go rewrite addresses some of the Python-specific concerns. Running Authentik with proper reverse proxy configuration (TLS termination, rate limiting) mitigates most risks.

For production deployments, all three require careful configuration of TLS, rate limiting on login endpoints, and monitoring of failed authentication attempts. The self-hosted advantage is that you control the monitoring and incident response — there's no dependency on a vendor's security team.

Migration Guide

Migrating from Auth0 to Authentik is the most common migration pattern in 2026. The key steps are: export user data from Auth0 (Auth0 provides bulk export), import users into Authentik using the SCIM API or direct database import, update application OIDC configuration to point to Authentik's endpoints, and test all authentication flows. The main challenge is migrating password hashes — Auth0 uses bcrypt, and Authentik supports bcrypt import. Users who haven't logged in since the migration will need to reset passwords.

Migrating from Keycloak to Zitadel is a common upgrade path for teams frustrated with Keycloak's configuration complexity. Keycloak's realm concept maps to Zitadel's organization concept, and the migration primarily involves recreating application registrations and importing users.

Adding Casdoor to an existing authentication system is often a complementary deployment rather than a replacement — use your existing OIDC provider for authentication and Casdoor's Casbin integration for fine-grained authorization decisions. This hybrid approach is common in organizations that have mature authentication infrastructure but need to add complex permission logic.

Final Verdict 2026

Authentik is the best choice for the widest range of self-hosted IAM use cases. Its proxy mode, comprehensive integration ecosystem, and flexible flow engine cover scenarios that Zitadel and Casdoor can't handle. The higher resource usage (~300MB memory) is acceptable for any server with 2GB+ RAM.

Zitadel is the best choice for B2B SaaS products that need multi-tenant organization management from the start. Its clean OIDC implementation, Kubernetes operator, and organization-centric data model make it the most developer-friendly option for new projects.

Casdoor is the right choice when complex authorization policies are the primary requirement. As a pure authentication solution, it's less polished than Authentik or Zitadel. As an authentication + fine-grained authorization platform, it's uniquely capable.

Methodology

Data sourced from GitHub repositories (star counts as of February 2026), official documentation, Docker Hub image sizes, and community benchmarks from self-hosted server forums (r/selfhosted, awesome-selfhosted). Memory usage measurements from community-reported Docker stats. Feature availability verified from official documentation and GitHub issue trackers.

Related: better-auth vs Lucia vs NextAuth 2026 for application-level auth libraries that integrate with IAM providers, Best Next.js Auth Solutions 2026 for auth in Next.js specifically, and Best JavaScript Testing Frameworks 2026 for testing auth flows in your applications.

Zitadel vs Casdoor vs Authentik: IAM 2026

Zitadel vs Casdoor vs Authentik: Open Source IAM in 2026

TL;DR

Key Takeaways

Why Self-Hosted IAM?

Zitadel: Cloud-Native Identity for SaaS

Docker Compose Setup

OIDC Integration (Node.js)

Zitadel Management API (Multi-Tenancy)

Zitadel Actions (Custom Logic)

Casdoor: Access Control Meets Identity

Docker Compose Setup

OIDC Integration

Casbin Permission Policies

ABAC (Attribute-Based Access Control)

Authentik: The Enterprise-Grade All-Rounder

Docker Compose Setup

OIDC Provider Integration

Authentik Proxy Mode (SSO for Legacy Apps)

Flows and Stages (Custom Auth Flows)

Feature Comparison

When to Use Each

Ecosystem & Community

Real-World Adoption

Developer Experience Deep Dive

Security Considerations

Migration Guide

Final Verdict 2026

Methodology

The 2026 JavaScript Stack Cheatsheet