head to head · open source
Keycloak vs cas
Keycloak has 37,657 GitHub stars, 9,129 forks, 3,292 open issues and last shipped yesterday. cas has 11,394 stars, 3,955 forks, 17 open issues and last shipped yesterday. Keycloak leads on adoption by 230% (37,657 vs 11,394 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 | ★ 38K | ★ 11K |
| License | Apache-2.0 | Apache-2.0 |
| Written in | Java | Java |
| Last push | 2026-11-02 | 2026-11-02 |
| Forks | ⑂ 9.1K | ⑂ 4.0K |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick Keycloak if
- You weight community size — 38K 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
Open Source Identity and Access Management Add authentication to applications and secure services with minimum effort. No need to deal with storing users or authenticating users. Keycloak provides user federation, strong authentication, user management, fine grained authorization, and more. Help and Documentation Documentation User Mailing List Mailing list for help and general questions about Keycloak Join keycloak for general questions, or keycloak dev on Slack for design and development discussions, by creating an account at Reporting Security Vulnerabilities If you have found a security vulnerability, please…
read the full Keycloak overview →
About cas
Central Authentication Service (CAS) [ ][casslack] [ ][cassupport] Introduction Welcome to the home of the [Central Authentication Service project][apereocas], more commonly referred to as CAS. CAS is an enterprise multilingual identity provider and single sign on solution for the web and attempts to be a comprehensive platform for your authentication and authorization needs. CAS is an open and well documented authentication protocol. The primary implementation of the protocol is an open source Java server component by the same name hosted here, with support for a plethora of additional authentication protocols…
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Frequently asked questions
Is Keycloak or cas more popular?
Keycloak has 37,657 GitHub stars and cas has 11,394. 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 (37,657 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.