head to head · open source
Zitadel vs cas
Zitadel has 15,507 GitHub stars, 1,416 forks, 1,171 open issues and last shipped 2 days ago. cas has 11,394 stars, 3,955 forks, 17 open issues and last shipped yesterday. Zitadel leads on adoption by 36% (15,507 vs 11,394 stars). Zitadel is written in Go under AGPL-3.0; cas is written in Java under Apache-2.0. Zitadel has attracted 9% as many forks as stars, cas 35%. cas was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 4 topic tags (authentication, authorization, mfa, 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.
← all 20902 open source comparisons
Side by side
| Zitadel | cas | |
|---|---|---|
| GitHub stars | ★ 16K | ★ 11K |
| License | AGPL-3.0 | Apache-2.0 |
| Written in | Go | Java |
| Last push | 2026-11-03 | 2026-11-04 |
| Forks | ⑂ 1.4K | ⑂ 4.0K |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick Zitadel if
- You weight community size — 16K stars and counting
- You want the AGPL-3.0 license terms
- Your stack matches Go
- 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 Zitadel
The Identity Infrastructure for Developers ZITADEL is an open source identity and access management platform built for teams that need more than basic auth. Whether you're securing a SaaS product, building a B2B platform, or self hosting a production IAM stack — ZITADEL gives you everything out of the box: SSO, MFA, Passkeys, OIDC, SAML, SCIM, and a battle tested multi tenancy model. No vendor lock in. No compromise on control. Just a robust, API first identity platform you can own. 🏡 Website 💬 Chat 📋 Docs 🧑💻 Blog 📞 Contact Why ZITADEL We built ZITADEL to handle the hardest IAM challenges at scale —…
read the full Zitadel 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…
More in Security & Privacy
Related comparisons
More Identity & Access Management (IAM) projects
Compare either of these against the rest of the Identity & Access Management (IAM) field.
Frequently asked questions
Is Zitadel or cas more popular?
Zitadel has 15,507 GitHub stars and cas has 11,394. Zitadel has the larger community by that measure.
Are Zitadel and cas free?
Both are open source. Zitadel is licensed under AGPL-3.0 and cas under Apache-2.0. Neither carries a licence fee.
What is the difference between Zitadel and cas?
Zitadel is written in Go 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, Zitadel or cas?
Choose Zitadel if you want the larger community (15,507 stars) or its AGPL-3.0 licence terms. Choose cas if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.