head to head · open source
calibre vs thorium-reader
calibre has 25,923 GitHub stars, 2,690 forks, 6 open issues and last shipped yesterday. thorium-reader has 2,872 stars, 237 forks, 206 open issues and last shipped yesterday. calibre leads on adoption by 803% (25,923 vs 2,872 stars). calibre is written in Python under GPL-3.0; thorium-reader is written in TypeScript under BSD-3-Clause. calibre has attracted 10% as many forks as stars, thorium-reader 8%. calibre was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 1 topic tag (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 | thorium-reader | |
|---|---|---|
| GitHub stars | ★ 26K | ★ 2.9K |
| License | GPL-3.0 | BSD-3-Clause |
| Written in | Python | TypeScript |
| Last push | 2026-09-17 | 2026-09-17 |
| Forks | ⑂ 2.7K | ⑂ 237 |
| 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 thorium-reader if
- You want the thorium-reader feature set and don't need the biggest community
- You prefer the BSD-3-Clause license terms
- Your stack matches TypeScript
- You evaluated both and thorium-reader 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 thorium-reader
Thorium Reader is a cross platform desktop reading application for Windows 10/10S, macOS, and Linux, based on the open source Readium Desktop toolkit. It lives in the content and publishing ecosystem, is categorized as Content & Publishing / Publishing, and is released under the BSD 3 Clause license. The repository reports 2,871 stars, 237 forks, and a last push on 2026 09 14.
read the full thorium-reader overview →
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Frequently asked questions
Is calibre or thorium-reader more popular?
calibre has 25,923 GitHub stars and thorium-reader has 2,872. calibre has the larger community by that measure.
Are calibre and thorium-reader free?
Both are open source. calibre is licensed under GPL-3.0 and thorium-reader under BSD-3-Clause. Neither carries a licence fee.
What is the difference between calibre and thorium-reader?
calibre is written in Python and thorium-reader in TypeScript. 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 thorium-reader?
Choose calibre if you want the larger community (25,923 stars) or its GPL-3.0 licence terms. Choose thorium-reader if its feature set, stack or BSD-3-Clause licence fits better. Both are self-hostable.