head to head · open source
koreader vs grimmory
koreader has 29,761 GitHub stars, 1,908 forks, 1,345 open issues and last shipped yesterday. grimmory has 4,373 stars, 324 forks, 243 open issues and last shipped yesterday. koreader leads on adoption by 581% (29,761 vs 4,373 stars). koreader is written in Lua under AGPL-3.0; grimmory is written in Java under AGPL-3.0. koreader has attracted 6% as many forks as stars, grimmory 7%. koreader was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 2 topic tags (cbz, epub), 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
| koreader | grimmory | |
|---|---|---|
| GitHub stars | ★ 30K | ★ 4.4K |
| License | AGPL-3.0 | AGPL-3.0 |
| Written in | Lua | Java |
| Last push | 2026-09-17 | 2026-09-17 |
| Forks | ⑂ 1.9K | ⑂ 324 |
| 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 grimmory if
- You want the grimmory feature set and don't need the biggest community
- You prefer the AGPL-3.0 license terms
- Your stack matches Java
- You evaluated both and grimmory 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 grimmory
Grimmory is a self hosted digital library for ebooks, comics, documents, and audiobooks that runs on your own server under the AGPL 3.0 licence, built for readers who want their whole collection — files, metadata, reading progress, and sharing — in one place they control rather than spread across devices, apps, and cloud accounts.
read the full grimmory overview →
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Frequently asked questions
Is koreader or grimmory more popular?
koreader has 29,761 GitHub stars and grimmory has 4,373. koreader has the larger community by that measure.
Are koreader and grimmory free?
Both are open source. koreader is licensed under AGPL-3.0 and grimmory under AGPL-3.0. Neither carries a licence fee.
What is the difference between koreader and grimmory?
koreader is written in Lua and grimmory 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, koreader or grimmory?
Choose koreader if you want the larger community (29,761 stars) or its AGPL-3.0 licence terms. Choose grimmory if its feature set, stack or AGPL-3.0 licence fits better. Both are self-hostable.