Apereo CAS vs ZITADEL
A side-by-side comparison of two self-hosted identity & sso options — licensing, setup difficulty, resource needs, and what each one replaces.
ZITADEL
Cloud-native identity infrastructure with multi-tenancy built
| Feature | Apereo CAS | ZITADEL |
|---|---|---|
| Deploy effort | Under-an-hour setup | Under-an-hour setup |
| Health score | 93 · Excellent | 95 · Excellent |
| Category | Identity & SSO | Identity & SSO |
| License | Apache-2.0 | Apache-2.0 |
| Language | Java | Go |
| Setup difficulty | Hard | Medium |
| Min. RAM | 1,024 MB | 512 MB |
| Deployment | docker, kubernetes, bare-metal | docker, kubernetes, binary |
| GitHub stars | ★ 11,376 | ★ 15,083 |
| First released | 2004 | 2020 |
| Replaces | Okta, Ping Identity | Auth0, Okta, Firebase Auth |
What are Apereo CAS and ZITADEL?
Apereo CAS
Apereo CAS is an open-source, enterprise single sign-on solution and identity provider. Widely used in higher education, it supports the CAS protocol along with SAML, OAuth2 and OpenID Connect.
- CAS, SAML, OAuth2 and OIDC protocols
- Multi-factor authentication
- Pluggable authentication handlers
- Delegated and federated authentication
ZITADEL
ZITADEL is an open-source identity and access management platform built for multi-tenant applications. It offers OpenID Connect, OAuth2, SAML, passwordless login and a powerful management API.
- Multi-tenancy as a first-class concept
- Passwordless and FIDO2 authentication
- Event-sourced audit trail
- Comprehensive gRPC and REST APIs
Apereo CAS vs ZITADEL: key differences
Apereo CAS is written in Java, while ZITADEL is built with Go. ZITADEL is the lighter option, starting around 512 MB of RAM against 1,024 MB for Apereo CAS. Apereo CAS is the more established project (first released 2004), while ZITADEL arrived in 2020.
Why pick each one
Choose Apereo CAS if…
- Mature SSO with broad protocol support
- Widely adopted in academia
Watch out for
- Configuration is involved
Choose ZITADEL if…
- Strong multi-tenant model
- Modern Go codebase
Watch out for
- Smaller community than Keycloak
Frequently asked questions
Is Apereo CAS or ZITADEL better?
ZITADEL is the stronger all-round pick: it has both the larger community and the simpler medium setup. Consider Apereo CAS if its specific feature set fits your needs better.
Are Apereo CAS and ZITADEL free and open-source?
Yes. Apereo CAS is licensed under Apache-2.0 and ZITADEL under Apache-2.0. Both can be self-hosted at no software cost.
Can I run Apereo CAS and ZITADEL with Docker?
Apereo CAS: yes. ZITADEL: yes.
Which is lighter on resources, Apereo CAS or ZITADEL?
ZITADEL has the smaller minimum footprint at 512 MB of RAM, compared to about 1,024 MB for Apereo CAS. Real-world usage depends on library size, user count, and enabled features.