head to head · open source
koreader vs hammer-editor
koreader has 29,761 GitHub stars, 1,908 forks, 1,345 open issues and last shipped yesterday. hammer-editor has 744 stars, 42 forks, 54 open issues and last shipped 2 days ago. koreader leads on adoption by 3,900% (29,761 vs 744 stars). koreader is written in Lua under AGPL-3.0; hammer-editor is written in Kotlin under MIT. koreader has attracted 6% as many forks as stars, hammer-editor 6%. koreader 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
| koreader | hammer-editor | |
|---|---|---|
| GitHub stars | ★ 30K | ★ 744 |
| License | AGPL-3.0 | MIT |
| Written in | Lua | Kotlin |
| Last push | 2026-09-17 | 2026-09-16 |
| Forks | ⑂ 1.9K | ⑂ 42 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick koreader if
- You weight community size — 30K stars and counting
- You want the AGPL-3.0 license terms
- Your stack matches Lua
- You value the larger contributor base for long-term maintenance
pick hammer-editor if
- You want the hammer-editor feature set and don't need the biggest community
- You prefer the MIT license terms
- Your stack matches Kotlin
- You evaluated both and hammer-editor fits your workflow better
About koreader
KOReader is a free, AGPL 3.0 licensed document viewer written in Lua that runs on e ink readers from Cervantes, Kindle, Kobo and PocketBook, on reMarkable, and on Android and desktop Linux, aimed at readers who want broader format support, finer typesetting control and better performance than the reading software shipped with their device.
read the full koreader overview →
About hammer-editor
Hammer is a free, open source, local first story editor for writers, built in Kotlin with Compose Multiplatform and shipped for Android, iOS, Windows, Linux and macOS, so a single draft stays with its author across phone and desktop.
read the full hammer-editor overview →
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Frequently asked questions
Is koreader or hammer-editor more popular?
koreader has 29,761 GitHub stars and hammer-editor has 744. koreader has the larger community by that measure.
Are koreader and hammer-editor free?
Both are open source. koreader is licensed under AGPL-3.0 and hammer-editor under MIT. Neither carries a licence fee.
What is the difference between koreader and hammer-editor?
koreader is written in Lua and hammer-editor in Kotlin. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, koreader or hammer-editor?
Choose koreader if you want the larger community (29,761 stars) or its AGPL-3.0 licence terms. Choose hammer-editor if its feature set, stack or MIT licence fits better. Both are self-hostable.