head to head · open source
Keycloak vs cas
Keycloak has 36,855 GitHub stars, 8,942 forks, 3,292 open issues and last shipped yesterday. cas has 11,366 stars, 3,959 forks, 17 open issues and last shipped yesterday. Keycloak leads on adoption by 224% (36,855 vs 11,366 stars). Keycloak is written in Java under Apache-2.0; cas is written in Java under Apache-2.0. Keycloak has attracted 24% as many forks as stars, cas 35%. Keycloak was the more recently maintained of the two, and both are self-hostable with no licence fee.
Two open source projects, one decision. Both are free and self-hostable — the differences are community size, license terms, language stack and release pace.
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Side by side
| Keycloak | cas | |
|---|---|---|
| GitHub stars | ★ 37K | ★ 11K |
| License | Apache-2.0 | Apache-2.0 |
| Written in | Java | Java |
| Last push | 2026-09-18 | 2026-09-18 |
| Forks | ⑂ 8.9K | ⑂ 4.0K |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick Keycloak if
- You weight community size — 37K stars and counting
- You want the Apache-2.0 license terms
- Your stack matches Java
- You value the larger contributor base for long-term maintenance
pick cas if
- You want the cas feature set and don't need the biggest community
- You prefer the Apache-2.0 license terms
- Your stack matches Java
- You evaluated both and cas fits your workflow better
About Keycloak
Keycloak is an open source identity and access management server, written in Java and licensed under Apache 2.0, that adds authentication and access control to applications and services, and it is intended for teams and organisations that want to own their user store rather than rent one.
read the full Keycloak overview →
About cas
Apereo CAS is the open source Java server that implements the Central Authentication Service protocol and serves as an enterprise identity provider and single sign on platform for the web, aimed at organizations that need one authentication and authorization layer across many applications.
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Frequently asked questions
Is Keycloak or cas more popular?
Keycloak has 36,855 GitHub stars and cas has 11,366. Keycloak has the larger community by that measure.
Are Keycloak and cas free?
Both are open source. Keycloak is licensed under Apache-2.0 and cas under Apache-2.0. Neither carries a licence fee.
What is the difference between Keycloak and cas?
Keycloak is written in Java and cas in Java. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, Keycloak or cas?
Choose Keycloak if you want the larger community (36,855 stars) or its Apache-2.0 licence terms. Choose cas if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.