head to head · open source
calibre vs citadel
calibre has 25,923 GitHub stars, 2,690 forks, 6 open issues and last shipped yesterday. citadel has 1,276 stars, 20 forks, 10 open issues and last shipped yesterday. calibre leads on adoption by 1,932% (25,923 vs 1,276 stars). calibre is written in Python under GPL-3.0; citadel is written in Rust under MIT. calibre has attracted 10% as many forks as stars, citadel 2%. citadel was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 4 topic tags (calibre, ebook, ebook-manager, 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
| calibre | citadel | |
|---|---|---|
| GitHub stars | ★ 26K | ★ 1.3K |
| License | GPL-3.0 | MIT |
| Written in | Python | Rust |
| Last push | 2026-09-17 | 2026-09-17 |
| Forks | ⑂ 2.7K | ⑂ 20 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick calibre if
- You weight community size — 26K stars and counting
- You want the GPL-3.0 license terms
- Your stack matches Python
- You value the larger contributor base for long-term maintenance
pick citadel if
- You want the citadel feature set and don't need the biggest community
- You prefer the MIT license terms
- Your stack matches Rust
- You evaluated both and citadel fits your workflow better
About calibre
calibre is the official source code repository for the calibre e book manager, an open source application written in Python and released under GPL 3.0. It lives in the content and publishing ecosystem as a desktop tool for books, and it is cross platform, running on Linux, Windows and macOS. The project has been hosted on GitHub for roughly thirteen years, carries about 25,900 stars and 2,683 forks, and its home on the web is calibre ebook.com, where an About page and a screenshots page document it further.
read the full calibre overview →
About citadel
Citadel is a desktop application for managing ebook libraries, written in Rust and released under the MIT license. It is positioned inside the Calibre ecosystem as a backwards compatible manager for ebook collections, with the stated goal that Calibre must be able to read any library that Citadel has edited. The project targets users who want a faster and easier to use interface for organizing ebooks, especially epub files, without replacing the Calibre library format.
read the full citadel overview →
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Frequently asked questions
Is calibre or citadel more popular?
calibre has 25,923 GitHub stars and citadel has 1,276. calibre has the larger community by that measure.
Are calibre and citadel free?
Both are open source. calibre is licensed under GPL-3.0 and citadel under MIT. Neither carries a licence fee.
What is the difference between calibre and citadel?
calibre is written in Python and citadel in Rust. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, calibre or citadel?
Choose calibre if you want the larger community (25,923 stars) or its GPL-3.0 licence terms. Choose citadel if its feature set, stack or MIT licence fits better. Both are self-hostable.