head to head · open source
opa vs Harden-Windows-Security
opa has 12,256 GitHub stars, 1,686 forks, 310 open issues and last shipped yesterday. Harden-Windows-Security has 4,746 stars, 337 forks, 5 open issues and last shipped yesterday. opa leads on adoption by 158% (12,256 vs 4,746 stars). opa is written in Go under Apache-2.0; Harden-Windows-Security is written in C# under MIT. opa has attracted 14% as many forks as stars, Harden-Windows-Security 7%. Harden-Windows-Security was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 1 topic tag (compliance), 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
| opa | Harden-Windows-Security | |
|---|---|---|
| GitHub stars | ★ 12K | ★ 4.7K |
| License | Apache-2.0 | MIT |
| Written in | Go | C# |
| Last push | 2026-09-19 | 2026-09-19 |
| Forks | ⑂ 1.7K | ⑂ 337 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick opa if
- You weight community size — 12K 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 Harden-Windows-Security if
- You want the Harden-Windows-Security feature set and don't need the biggest community
- You prefer the MIT license terms
- Your stack matches C#
- You evaluated both and Harden-Windows-Security fits your workflow better
About opa
Open Policy Agent (OPA) is an open source, general purpose policy engine that enables unified, context aware policy enforcement across the entire stack. It lives in the cloud native ecosystem as a graduated project in the Cloud Native Computing Foundation landscape, and it is written in Go under the Apache 2.0 license. Policy is expressed declaratively in the Rego language, and the project ships alongside a CLI, an HTTP REST API, a Go SDK, and editor tooling rather than as a single binary alone. The repository has been active for roughly eleven years, with 12,234 stars, 1,679 forks, and a last push dated 15 Septe…
About Harden-Windows-Security
Harden Windows Security is a GitHub repository and Windows focused security project written in C under the MIT license. It provides guides and tools for hardening Windows devices by using official, supported Microsoft methods rather than third party components. The project lives in the Windows and Microsoft security ecosystem, including Defender, BitLocker, firewall configuration, audit, encryption, compliance, enterprise security, and Intune.
read the full Harden-Windows-Security overview →
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Frequently asked questions
Is opa or Harden-Windows-Security more popular?
opa has 12,256 GitHub stars and Harden-Windows-Security has 4,746. opa has the larger community by that measure.
Are opa and Harden-Windows-Security free?
Both are open source. opa is licensed under Apache-2.0 and Harden-Windows-Security under MIT. Neither carries a licence fee.
What is the difference between opa and Harden-Windows-Security?
opa is written in Go and Harden-Windows-Security in C#. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, opa or Harden-Windows-Security?
Choose opa if you want the larger community (12,256 stars) or its Apache-2.0 licence terms. Choose Harden-Windows-Security if its feature set, stack or MIT licence fits better. Both are self-hostable.