---
source_url: "https://skycloak.io/blog/keycloak-vs-zitadel-comparison/"
title: "Keycloak vs Zitadel: Open-Source IAM Compared"
mirrored_at: 2026-08-12T13:02:27.882Z
host: skycloak.io
cited_in_42a: true
mirror_canonical: "https://index.42a.ai/skycloak.io/blog/keycloak-vs-zitadel-comparison/index"
---

> **Original source:** https://skycloak.io/blog/keycloak-vs-zitadel-comparison/

_Last updated: June 2026_

**Both Keycloak and Zitadel are open-source, self-hostable identity and access management platforms that support OIDC, OAuth 2.0, and SAML. Keycloak is a Java/Quarkus-based project licensed under Apache 2.0, backed by Red Hat, with a deep SPI extension model and the largest open-source IAM ecosystem available today. Zitadel is a Go-based platform built organizations-first, offering a modern gRPC/REST API, native multi-tenancy, and a built-in audit trail out of the box. Choose Keycloak when ecosystem maturity, enterprise integrations, and deep customizability matter most; choose Zitadel when you’re building a multi-tenant SaaS product and want an API-first experience with lower operational complexity.**

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Picking the wrong IAM platform can cost months of migration work. This guide compares Keycloak 26.x and Zitadel across licensing, architecture, multi-tenancy, protocols, extensibility, self-hosting, and ecosystem maturity, with comparison tables throughout.

## Licensing and Governance

Both platforms are released under the **Apache License 2.0**: fully open source, commercially usable, no copyleft obligations. Keycloak is sponsored by Red Hat/IBM with institutional long-term backing inside the CNCF ecosystem. Zitadel is backed by ZITADEL GmbH, a Swiss startup that moves faster but operates with a smaller core team. Neither platform withholds core features behind a paid license tier.

Keycloak

Zitadel

**License**

Apache 2.0

Apache 2.0

**Sponsor**

Red Hat / IBM

ZITADEL GmbH (Swiss)

**Business model**

Upstream open source; Red Hat sells enterprise support

Open-core SaaS cloud + enterprise support

**Self-host for free**

Yes

Yes

**Commercial hosting**

Third-party (e.g., Skycloak)

ZITADEL Cloud

## Architecture and Runtime

The runtime difference is one of the sharpest divides between the two platforms. Keycloak 26.x runs on **Quarkus (Java)**: a major improvement over the legacy WildFly base, with optional GraalVM native image support for faster startup and lower memory. The JVM deployment path remains most common in production. Zitadel is written in **Go** and ships as a single static binary: sub-second startup, low baseline memory, no JVM to tune.

Keycloak

Zitadel

**Language**

Java (Quarkus)

Go

**Deployment artifact**

Docker image / JVM JAR / native binary

Single Go binary / Docker image

**Database support**

PostgreSQL, MySQL/MariaDB, MSSQL, Oracle

PostgreSQL, CockroachDB

**High availability**

Infinispan cluster (embedded or external)

Built-in via PostgreSQL + stateless nodes

**Memory baseline**

Medium–high (JVM)

Low (Go)

**Startup time**

Seconds (Quarkus; native: sub-second)

Sub-second

**Configuration**

`kc.sh` CLI, environment variables, `keycloak.conf`

Environment variables, config file

Zitadel’s stateless nodes (all state in the database) simplify horizontal scaling. Keycloak’s Infinispan clustering gives finer session cache control but requires more operational attention at scale.

## Protocol Support

Both platforms cover the major enterprise protocols and are largely equivalent in this area.

Protocol

Keycloak

Zitadel

**OpenID Connect 1.0**

Full

Full

**OAuth 2.0 / 2.1**

Full

Full

**SAML 2.0**

Full (IdP + SP)

Partial (IdP only, no SP brokering)

**LDAP / Active Directory**

Full federation

Read-only sync

**Kerberos**

Yes (SPNEGO)

No

**SCIM 2.0**

Via extension / SPI

Native (partial)

**WebAuthn / Passkeys**

Yes

Yes

**Device Authorization Grant**

Yes

Yes

**Token Exchange**

Yes

Yes

The key gap: Keycloak supports SAML as both IdP and SP, so it can broker between a SAML upstream IdP (Ping, ADFS, legacy Okta) and an OIDC downstream client. Zitadel’s SAML support is IdP-only, it issues SAML assertions but can’t consume them from upstream sources. If SAML federation is a hard requirement, Keycloak is the only choice here. Our [comparison of open-source authentication platforms in 2026](https://skycloak.io/blog/open-source-authentication-comparison-2026/) covers this matrix across a broader set of tools.

## Multi-Tenancy Models

Multi-tenancy is where the platforms diverge most philosophically, and the model you choose shapes your data architecture for years.

**Keycloak** uses _realms_ as its primary isolation boundary: each realm is an independent namespace with its own users, clients, roles, IdPs, and auth flows. Keycloak 26.x added the **Organizations** feature, which layers a second tier of tenancy _within_ a realm for B2B SaaS scenarios. Our deep-dive on [multi-tenancy in Keycloak using the Organizations feature](https://skycloak.io/blog/multitenancy-in-keycloak-using-the-organizations-feature/) explains how this works in practice.

**Zitadel** was designed organizations-first. Its hierarchy, **Instance → Organization → Project → Application**: makes each tenant a first-class citizen with its own login policy, IdP, branding, and user pool. This maps naturally onto a SaaS product where each customer self-provisions their own account.

Keycloak

Zitadel

**Primary isolation unit**

Realm

Organization

**Multi-tenancy maturity**

Realms (stable); Organizations (GA in 26.x)

Organizations (core design, stable)

**Tenant provisioning API**

Realm admin REST API

Organization API (gRPC + REST)

**Per-tenant branding**

Per-realm themes

Per-organization branding

**Per-tenant IdP federation**

Per-realm IdP config

Per-organization IdP config

**Shared user pool across tenants**

Organizations feature (26.x)

Native (users linked to orgs)

**Best fit**

Enterprise SSO; federated identity; mixed workloads

B2B SaaS; multi-tenant API products

If you’re building a B2B SaaS product where each customer self-provisions an account and needs their own login page and IdP, Zitadel’s organization model is more natural. If you’re running a platform with a small number of large enterprise tenants, or if you need per-tenant SAML federation, Keycloak realms plus Organizations is the more proven path.

## Extensibility and Customization

Both platforms are extensible, but through very different mechanisms. Keycloak’s **SPI (Service Provider Interface)** system lets you extend nearly every layer: auth flows, user storage (custom databases, LDAP), token mappers, FreeMarker themes, and event listeners, all deployed as JAR files. Adding an SPI requires a Keycloak rebuild, but the ecosystem is mature and thousands of community SPIs exist on GitHub. Our [complete guide to Keycloak](https://skycloak.io/blog/what-is-keycloak-complete-guide/) covers what the SPI system can do in practice.

Zitadel uses **Actions**: JavaScript/TypeScript functions stored in the database and executed at runtime lifecycle hooks (pre-auth, post-auth, token creation). No rebuild required. The tradeoff: Actions are hook-based, not pluggable. You can’t replace Zitadel’s user store or build arbitrary auth flows the way Keycloak SPIs allow.

Keycloak

Zitadel

**Extension model**

SPI (Java JARs, build-time)

Actions (JS/TS, runtime)

**Custom auth flows**

Full (per-realm, arbitrarily complex)

Partial (hook-based)

**Custom user storage**

Yes (LDAP, custom DB via UserStorage SPI)

No (Zitadel owns the user store)

**Custom themes / branding**

FreeMarker themes, full CSS/HTML control

Per-org branding (logo, colors, limited templates)

**Admin API**

REST (comprehensive)

gRPC + REST (comprehensive)

**Extension ecosystem**

Large (community SPIs, Keycloak GitHub org)

Small but growing

## Audit Trail and Eventing

Zitadel is built on an **event-sourcing architecture**: every state change is recorded as an immutable event in the database. The result is a tamper-evident, replayable audit trail with zero configuration, a genuine advantage for compliance-heavy environments (HIPAA, SOC 2, financial services).

Keycloak’s audit system runs through the **EventListener SPI**. Events are stored in the database with configurable retention and can be forwarded to Kafka, Elasticsearch, or a SIEM via listener providers. It’s flexible and production-proven, but reaching the same depth of audit coverage Zitadel provides out of the box requires deliberate setup. For most enterprise deployments, a properly configured Keycloak event pipeline meets audit requirements. Our [Keycloak vs FusionAuth comparison](https://skycloak.io/blog/keycloak-vs-fusionauth-comparison/) also examines audit capabilities against another popular IAM alternative.

Keycloak

Zitadel

**Audit architecture**

Event database + EventListener SPI

Event sourcing (immutable event store)

**Default audit retention**

Configurable (days/events count)

All events retained by default

**Compliance-ready out of box**

Requires configuration

Yes

**External SIEM integration**

Via EventListener SPI

Via event stream / webhook

**Event replay**

No

Yes

## Self-Hosting: Deployment and Operational Burden

This is where Keycloak’s honest weakness shows. Running Keycloak in production requires real operational investment: Infinispan cluster management, JVM memory tuning, database connection pooling, and theme rebuilds whenever you add a custom SPI. Teams that underestimate this complexity end up with flaky clusters under load.

That’s not a reason to avoid Keycloak, it’s a reason to size your DevOps capacity accurately, or consider a managed service. Our post on [self-hosted vs managed authentication cost](https://skycloak.io/blog/self-hosted-vs-managed-authentication-cost/) breaks down where the hidden costs live. Zitadel’s stateless Go binary sidesteps most of these concerns: no JVM tuning, smaller footprint, and horizontal scaling against PostgreSQL without cluster coordination state.

Keycloak

Zitadel

**Container size (approx.)**

~500 MB+ (JVM)

~50–80 MB (Go binary)

**HA complexity**

Medium–high (Infinispan cluster)

Low (stateless + PostgreSQL)

**Database dependencies**

PostgreSQL/MySQL/MSSQL/Oracle

PostgreSQL or CockroachDB

**JVM tuning required**

Yes

No

**Kubernetes operator**

Yes (Keycloak Operator, CNCF)

Yes (Zitadel Kubernetes chart)

**Managed hosting available**

Yes (Skycloak, others)

Yes (ZITADEL Cloud)

**Helm chart**

Yes

Yes

## Ecosystem and Community Maturity

Keycloak has been in active development since 2014 with a CNCF footprint, Terraform providers, Ansible roles, Kubernetes operators, and adapters for Java, Node.js, Python, Go, and .NET. The community knowledge base, Stack Overflow threads, blog posts, production war stories, is enormous. Zitadel’s first public release was around 2020; its documentation is clean and SDKs cover major languages, but the community is orders of magnitude smaller. Zitadel’s ecosystem is adequate for greenfield SaaS builds; for complex enterprise integrations, Keycloak’s depth is a genuine advantage.

## Head-to-Head Feature Summary

Feature

Keycloak 26.x

Zitadel (latest)

**License**

Apache 2.0

Apache 2.0

**Language**

Java/Quarkus

Go

**OIDC / OAuth 2.0**

Full

Full

**SAML 2.0 (IdP + SP)**

Full

IdP only

**Multi-tenancy**

Realms + Organizations

Organizations (native)

**Extensibility**

Deep (SPI system)

Moderate (Actions)

**Audit trail**

Configurable

Event-sourced (built-in)

**LDAP/AD federation**

Full

Read-only sync

**Passkeys / WebAuthn**

Yes

Yes

**Admin API**

REST

gRPC + REST

**Managed hosting**

Third-party (e.g., Skycloak)

ZITADEL Cloud

**Community size**

Large

Small–medium

**Self-host complexity**

Medium–high

Low–medium

**Best for**

Enterprise SSO, complex integrations, SAML-heavy

Multi-tenant SaaS, API-first, modern stacks

## When to Choose Keycloak

Choose Keycloak if you need SAML SP support to federate with upstream IdPs (Ping, ADFS, legacy Okta), custom user storage via the UserStorage SPI, deep authentication flow customization, or the widest possible enterprise integration ecosystem. It’s also the right call when token mapper flexibility or long-term community support matters most.

## When to Choose Zitadel

Choose Zitadel if you’re building a multi-tenant SaaS product where each customer needs their own organization, IdP, and branding out of the box. It’s also the better fit if you want a gRPC-first API, an event-sourced compliance trail with zero configuration, or a lower-complexity self-hosted footprint on limited DevOps capacity.

## Frequently asked questions

### Is Zitadel a good Keycloak alternative?

Zitadel is a credible alternative for multi-tenant B2B SaaS products that need organizations as a first-class primitive, a modern gRPC API, and lower self-hosting complexity. For enterprise deployments requiring SAML SP support, LDAP federation, or Keycloak’s deep SPI ecosystem, Keycloak remains the stronger choice. The right answer depends on your architecture and operational capacity.

### Is Zitadel open source?

Yes. Zitadel is open source under the Apache License 2.0. You can self-host it for free with no feature restrictions. ZITADEL GmbH offers a commercial cloud and support contracts, but the open-source license doesn’t cap features between community and commercial versions, unlike some dual-license competitors.

### Keycloak vs Zitadel: which is better for multi-tenant SaaS?

Zitadel has a structural advantage here: organizations were a core design decision, not a late addition. Each org gets its own IdP, branding, login policy, and user pool by default. Keycloak’s Organizations feature (GA in 26.x) works well for existing deployments, but Zitadel’s model is more deeply integrated across the platform. For greenfield SaaS, Zitadel is more natural. For existing Keycloak users, Organizations covers most B2B scenarios adequately.

### Does Zitadel support SAML?

Zitadel supports SAML 2.0 as an identity provider, it can issue SAML assertions to service providers that require SAML. However, Zitadel does not support acting as a SAML service provider, meaning it can’t consume SAML assertions from upstream IdPs to broker identity. If your environment requires federating with a legacy SAML IdP (ADFS, Ping Identity, legacy Okta), Keycloak is the appropriate choice. Most modern cloud environments that are OIDC-only won’t encounter this limitation.

### Which is easier to self-host: Keycloak or Zitadel?

Zitadel is generally easier to self-host for small and medium deployments. Its Go binary has a lower memory footprint, stateless nodes simplify horizontal scaling, and there’s no JVM to tune or Infinispan cluster to manage. Keycloak’s Quarkus migration significantly improved its self-hosting story compared to WildFly, but it still requires more operational knowledge for production clustering and performance tuning. Both platforms support Kubernetes via Helm charts and operators.

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## The managed Keycloak option

If Keycloak’s ecosystem is what you need but the self-hosting overhead isn’t something your team wants to own, managed Keycloak is worth a look. Skycloak handles the infrastructure, security patches, Infinispan cluster management, and version upgrades, while you keep full access to Keycloak’s SPIs, auth flows, and customizations.

See our [pricing page](https://skycloak.io/pricing/) or learn more about [what managed Keycloak hosting includes](https://skycloak.io/hosting/).