head to head · open source
hydra vs pac4j
hydra has 17,581 GitHub stars, 1,609 forks, 98 open issues and last shipped 2 months ago. pac4j has 2,530 stars, 711 forks, 5 open issues and last shipped yesterday. hydra leads on adoption by 595% (17,581 vs 2,530 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 | 2026-09-30 |
| Forks | ⑂ 1.6K | ⑂ 711 |
| 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
Ory Hydra is an OpenID Certified OpenID Connect and OAuth 2.1 provider written in Go and licensed under Apache 2.0, built for teams that need standards compliant token issuance, client management, and consent flows while user accounts stay in their own existing identity system.
read the full hydra overview →
About pac4j
pac4j is a security engine for Java that adds authentication and authorization — across OpenID Connect, SAML 2, CAS, OAuth, JWT, LDAP and more — to any Java framework through one shared API.
read the full pac4j overview →
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Frequently asked questions
Is hydra or pac4j more popular?
hydra has 17,581 GitHub stars and pac4j has 2,530. 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 (17,581 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.