Apereo CAS vs Ipsilon
A side-by-side comparison of two self-hosted identity & sso options — licensing, setup difficulty, resource needs, and what each one replaces.
| Feature | Apereo CAS | Ipsilon |
|---|---|---|
| Deploy effort | Under-an-hour setup | Read-the-docs project |
| Category | Identity & SSO | Identity & SSO |
| License | Apache-2.0 | GPL-3.0 |
| Language | Java | Python |
| Setup difficulty | Hard | Hard |
| Min. RAM | 1,024 MB | 512 MB |
| Deployment | docker, kubernetes, bare-metal | bare-metal, source |
| GitHub stars | ★ 11,374 | ★ 80 |
| First released | 2004 | 2014 |
| Replaces | Okta, Ping Identity | Okta, PingFederate |
What are Apereo CAS and Ipsilon?
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
Ipsilon
Ipsilon is an identity provider service that supports SAML and OpenID for federated single sign-on. It plugs into existing authentication backends like FreeIPA to centralize login for web applications.
- SAML identity provider
- OpenID support
- FreeIPA integration
- Pluggable backends
Apereo CAS vs Ipsilon: key differences
Apereo CAS is written in Java, while Ipsilon is built with Python. Licensing differs — Apache-2.0 for Apereo CAS versus GPL-3.0 for Ipsilon. Ipsilon 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 Ipsilon arrived in 2014. Apereo CAS has the considerably larger community, at 11,374 GitHub stars versus 80. Apereo CAS lists first-class Docker deployment; Ipsilon does not.
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 Ipsilon if…
- Good FreeIPA companion
- Federation focused
Watch out for
- Small community
- Limited recent activity
Frequently asked questions
Is Apereo CAS or Ipsilon better?
Neither is universally better. Apereo CAS has the larger community; both share a hard setup difficulty, so the decision comes down to features and licensing.
Are Apereo CAS and Ipsilon free and open-source?
Yes. Apereo CAS is licensed under Apache-2.0 and Ipsilon under GPL-3.0. Both can be self-hosted at no software cost.
Can I run Apereo CAS and Ipsilon with Docker?
Apereo CAS: yes. Ipsilon: check the project docs for container support.
Which is lighter on resources, Apereo CAS or Ipsilon?
Ipsilon 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.