head to head · open source
hydra vs pac4j
hydra has 17,664 GitHub stars, 1,622 forks, 98 open issues and last shipped 4 months ago. pac4j has 2,539 stars, 710 forks, 5 open issues and last shipped yesterday. hydra leads on adoption by 596% (17,664 vs 2,539 stars). hydra is written in Go under Apache-2.0; pac4j is written in Java under Apache-2.0. hydra 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 4 topic tags (authorization, identity, oauth, 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
| hydra | pac4j | |
|---|---|---|
| GitHub stars | ★ 18K | ★ 2.5K |
| License | Apache-2.0 | Apache-2.0 |
| Written in | Go | Java |
| Last push | 2026-07-29 | 2026-11-14 |
| Forks | ⑂ 1.6K | ⑂ 710 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick hydra if
- You weight community size — 18K stars and counting
- You want the Apache-2.0 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 hydra
Chat · Discussions · Newsletter · Docs · Try Ory Network · Jobs Ory Hydra is a hardened, OpenID Certified OAuth 2.0 Server and OpenID Connect Provider optimized for low latency, high throughput, and low resource consumption. It connects to your existing identity provider through a login and consent app, giving you absolute control over the user interface and experience. What is Ory Hydra? Why Ory Hydra OAuth2 and OpenID Connect: Open Standards OpenID Connect Certified Deployment options Use Ory Hydra on the Ory Network Self host Ory Hydra Quickstart Who is using Ory Hydra Ecosystem Ory Kratos: Identity and User…
read the full hydra 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 hydra or pac4j more popular?
hydra has 17,664 GitHub stars and pac4j has 2,539. hydra has the larger community by that measure.
Are hydra and pac4j free?
Both are open source. hydra is licensed under Apache-2.0 and pac4j under Apache-2.0. Neither carries a licence fee.
What is the difference between hydra and pac4j?
hydra 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, hydra or pac4j?
Choose hydra if you want the larger community (17,664 stars) or its Apache-2.0 licence terms. Choose pac4j if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.