head to head · open source
Authentik vs cas
Authentik has 25,627 GitHub stars, 2,024 forks, 1,074 open issues and last shipped yesterday. cas has 11,366 stars, 3,959 forks, 17 open issues and last shipped yesterday. Authentik leads on adoption by 125% (25,627 vs 11,366 stars). Authentik is written in Python under a custom or non-standard licence; cas is written in Java under Apache-2.0. Authentik has attracted 8% as many forks as stars, cas 35%. Authentik was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 3 topic tags (authentication, authorization, oauth2), so they are genuine substitutes rather than adjacent tools.
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
| Authentik | cas | |
|---|---|---|
| GitHub stars | ★ 26K | ★ 11K |
| License | Custom / other | Apache-2.0 |
| Written in | Python | Java |
| Last push | 2026-09-18 | 2026-09-18 |
| Forks | ⑂ 2.0K | ⑂ 4.0K |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick Authentik if
- You weight community size — 26K stars and counting
- You want the Custom / other license terms
- Your stack matches Python
- 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 Authentik
Authentik is an open source Identity Provider (IdP) built for modern single sign on (SSO) workflows. It operates in the identity and access management (IAM) ecosystem, offering a self hosted alternative to commercial solutions like Auth0, Okta, and Entra ID. The project is written in Python and distributed under a mixed MIT/CC BY SA/enterprise license model, with a core open source offering and an enterprise tier for advanced features and support.
read the full Authentik 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 Authentik or cas more popular?
Authentik has 25,627 GitHub stars and cas has 11,366. Authentik has the larger community by that measure.
Are Authentik and cas free?
Both are open source. Authentik has no licence declared in this registry, and cas is licensed under Apache-2.0. Both are free to self-host.
What is the difference between Authentik and cas?
Authentik is written in Python 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, Authentik or cas?
Choose Authentik if you want the larger community (25,627 stars) or its Custom / other licence terms. Choose cas if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.