head to head · open source
Zitadel vs pac4j
Zitadel has 15,585 GitHub stars, 1,432 forks, 1,171 open issues and last shipped 2 days ago. pac4j has 2,539 stars, 710 forks, 5 open issues and last shipped yesterday. Zitadel leads on adoption by 514% (15,585 vs 2,539 stars). Zitadel is written in Go under AGPL-3.0; pac4j is written in Java under Apache-2.0. Zitadel has attracted 9% as many forks as stars, pac4j 28%. pac4j was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 6 topic tags (authentication, authorization, identity, 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
| Zitadel | pac4j | |
|---|---|---|
| GitHub stars | ★ 16K | ★ 2.5K |
| License | AGPL-3.0 | Apache-2.0 |
| Written in | Go | Java |
| Last push | 2026-11-13 | 2026-11-14 |
| Forks | ⑂ 1.4K | ⑂ 710 |
| 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 pac4j if
- You want the pac4j 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 pac4j 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 pac4j
The security engine for Java: one API to add OpenID Connect, SAML, CAS, OAuth, JWT, LDAP... authentication and authorization to any Java framework. Documentation • Quick start • Frameworks • Concepts • Help ✨ Why pac4j? 🧩 One security engine, every framework : the same concepts and the same configuration for Spring Boot, Jakarta EE, Play, Vert.x, Javalin, JAX RS and many more. 🔐 All the major protocols : OpenID Connect, SAML 2, CAS, OAuth 1.0 & 2.0, JWT, LDAP, Kerberos, HTTP... Log in with Keycloak, Microsoft Entra ID, Google, GitHub, Okta, Auth0, any SAML IdP or CAS server. 🛡️…
read the full pac4j overview →
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Frequently asked questions
Is Zitadel or pac4j more popular?
Zitadel has 15,585 GitHub stars and pac4j has 2,539. Zitadel has the larger community by that measure.
Are Zitadel and pac4j free?
Both are open source. Zitadel is licensed under AGPL-3.0 and pac4j under Apache-2.0. Neither carries a licence fee.
What is the difference between Zitadel and pac4j?
Zitadel is written in Go and pac4j 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 pac4j?
Choose Zitadel if you want the larger community (15,585 stars) or its AGPL-3.0 licence terms. Choose pac4j if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.