Apereo CAS vs Ory Hydra
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 | Ory Hydra |
|---|---|---|
| Deploy effort | Under-an-hour setup | Under-an-hour setup |
| Health score | 93 · Excellent | 90 · Excellent |
| Category | Identity & SSO | Identity & SSO |
| License | Apache-2.0 | Apache-2.0 |
| Language | Java | Go |
| Setup difficulty | Hard | Hard |
| Min. RAM | 1,024 MB | 256 MB |
| Deployment | docker, kubernetes, bare-metal | docker, kubernetes, binary |
| GitHub stars | ★ 11,376 | ★ 17,563 |
| First released | 2004 | 2015 |
| Replaces | Okta, Ping Identity | Okta, Auth0 |
What are Apereo CAS and Ory Hydra?
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
Ory Hydra
Ory Hydra is an OpenID Certified OAuth 2.0 and OpenID Connect provider. It is built to integrate with any existing identity system and issues tokens without managing user accounts itself.
- OpenID Certified implementation
- Low memory footprint
- Bring your own login and consent UI
- Scales horizontally
Apereo CAS vs Ory Hydra: key differences
Apereo CAS is written in Java, while Ory Hydra is built with Go. Ory Hydra is the lighter option, starting around 256 MB of RAM against 1,024 MB for Apereo CAS. Apereo CAS is the more established project (first released 2004), while Ory Hydra arrived in 2015.
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 Ory Hydra if…
- Security focused and certified
- Integrates with any user store
Watch out for
- Only handles OAuth, not user management
Frequently asked questions
Is Apereo CAS or Ory Hydra better?
Neither is universally better. Ory Hydra has the larger community; both share a hard setup difficulty, so the decision comes down to features and licensing.
Are Apereo CAS and Ory Hydra free and open-source?
Yes. Apereo CAS is licensed under Apache-2.0 and Ory Hydra under Apache-2.0. Both can be self-hosted at no software cost.
Can I run Apereo CAS and Ory Hydra with Docker?
Apereo CAS: yes. Ory Hydra: yes.
Which is lighter on resources, Apereo CAS or Ory Hydra?
Ory Hydra has the smaller minimum footprint at 256 MB of RAM, compared to about 1,024 MB for Apereo CAS. Real-world usage depends on library size, user count, and enabled features.