head to head · open source
Authentik vs cas
Authentik has 26,209 GitHub stars, 2,099 forks, 1,074 open issues and last shipped yesterday. cas has 11,394 stars, 3,955 forks, 17 open issues and last shipped yesterday. Authentik leads on adoption by 130% (26,209 vs 11,394 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 | 2026-11-02 | 2026-11-02 |
| Forks | ⑂ 2.1K | ⑂ 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
What is authentik? authentik is an open source Identity Provider (IdP) for modern SSO. It supports SAML, OAuth2/OIDC, LDAP, RADIUS, and more, designed for self hosting from small labs to large production clusters. Our enterprise offering is available for organizations to securely replace existing IdPs such as Okta, Auth0, Entra ID, and Ping Identity for robust, large scale identity management. Installation Docker Compose: recommended for small/test setups. See the documentation. Kubernetes (Helm Chart): recommended for larger setups. See the documentation and the Helm chart repository. AWS CloudFormation: deploy…
read the full Authentik 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 Authentik or cas more popular?
Authentik has 26,209 GitHub stars and cas has 11,394. 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 (26,209 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.