head to head · open source
Harness vs mill
Harness has 38,378 GitHub stars, 3,397 forks, 106 open issues and last shipped 2 days ago. mill has 2,792 stars, 447 forks, 272 open issues and last shipped yesterday. Harness leads on adoption by 1,275% (38,378 vs 2,792 stars). Harness is written in Go under Apache-2.0; mill is written in Scala under MIT. Harness has attracted 9% as many forks as stars, mill 16%. mill was the more recently maintained of the two, and both are self-hostable with no licence fee.
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
| Harness | mill | |
|---|---|---|
| GitHub stars | ★ 38K | ★ 2.8K |
| License | Apache-2.0 | MIT |
| Written in | Go | Scala |
| Last push | 2026-09-16 | 2026-09-17 |
| Forks | ⑂ 3.4K | ⑂ 447 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick Harness if
- You weight community size — 38K 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 mill if
- You want the mill feature set and don't need the biggest community
- You prefer the MIT license terms
- Your stack matches Scala
- You evaluated both and mill fits your workflow better
About Harness
Harness Open Source is an Apache 2.0, Go based developer platform that combines Git source control management, CI/CD pipelines, Gitspaces hosted development environments and artifact registries into one self hostable system for engineering teams that want end to end software delivery without stitching four separate products together.
read the full Harness overview →
About mill
Mill build tool. Java Scala Kotlin projects. Lives in JVM ecosystem. Category Developer Tools / Build & Deployment. License MIT. Language Scala. Homepage mill build.org. Stable version 1.1.9. Maven Central artifact com.lihaoyi/mill dist shown. Badge shows stable version and unstable dev version. Repo age 9 years. Last push 2026 09 14T12:22:46Z. Stars 2791. Forks 447. Open issues 272. Contributors not listed. GitHub description repeats tagline. README links current documentation site. README includes quick example.
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Frequently asked questions
Is Harness or mill more popular?
Harness has 38,378 GitHub stars and mill has 2,792. Harness has the larger community by that measure.
Are Harness and mill free?
Both are open source. Harness is licensed under Apache-2.0 and mill under MIT. Neither carries a licence fee.
What is the difference between Harness and mill?
Harness is written in Go and mill in Scala. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, Harness or mill?
Choose Harness if you want the larger community (38,378 stars) or its Apache-2.0 licence terms. Choose mill if its feature set, stack or MIT licence fits better. Both are self-hostable.