Apereo CAS vs Gluu Flex
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 | Gluu Flex |
|---|---|---|
| Deploy effort | Under-an-hour setup | Under-an-hour setup |
| Health score | 93 · Excellent | 69 · Good |
| Category | Identity & SSO | Identity & SSO |
| License | Apache-2.0 | Apache-2.0 |
| Language | Java | TypeScript |
| Setup difficulty | Hard | Hard |
| Min. RAM | 1,024 MB | 4,096 MB |
| Deployment | docker, kubernetes, bare-metal | docker, kubernetes, helm |
| GitHub stars | ★ 11,376 | ★ 31 |
| First released | 2004 | 2009 |
| Replaces | Okta, Ping Identity | Okta, Ping Identity |
What are Apereo CAS and Gluu Flex?
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
Gluu Flex
Gluu provides a self-hostable identity platform for single sign-on, multi-factor authentication, and access management built on open standards. It supports OAuth, OIDC, SAML, and FIDO2.
- Single sign-on
- OAuth, OIDC and SAML
- FIDO2 strong authentication
- Kubernetes deployment
Apereo CAS vs Gluu Flex: key differences
Apereo CAS is written in Java, while Gluu Flex is built with TypeScript. Apereo CAS is the lighter option, starting around 1,024 MB of RAM against 4,096 MB for Gluu Flex. Apereo CAS is the more established project (first released 2004), while Gluu Flex arrived in 2009. Apereo CAS has the considerably larger community, at 11,376 GitHub stars versus 31.
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 Gluu Flex if…
- Released under the Apache-2.0 license
- First-class Docker support for quick deployment
- Kubernetes-ready with Helm charts available
- Written in TypeScript
Frequently asked questions
Is Apereo CAS or Gluu Flex 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 Gluu Flex free and open-source?
Yes. Apereo CAS is licensed under Apache-2.0 and Gluu Flex under Apache-2.0. Both can be self-hosted at no software cost.
Can I run Apereo CAS and Gluu Flex with Docker?
Apereo CAS: yes. Gluu Flex: yes.
Which is lighter on resources, Apereo CAS or Gluu Flex?
Apereo CAS has the smaller minimum footprint at 1,024 MB of RAM, compared to about 4,096 MB for Gluu Flex. Real-world usage depends on library size, user count, and enabled features.