Keycloak vs Zitadel: Open-Source IAM Compared

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 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 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 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 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 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 or learn more about what managed Keycloak hosting includes.