head to head · open source
calibre vs HRConvert2
calibre has 25,923 GitHub stars, 2,690 forks, 6 open issues and last shipped yesterday. HRConvert2 has 1,369 stars, 82 forks, 2 open issues and last shipped 10 days ago. calibre leads on adoption by 1,794% (25,923 vs 1,369 stars). calibre is written in Python under GPL-3.0; HRConvert2 is written in PHP under GPL-3.0. calibre has attracted 10% as many forks as stars, HRConvert2 6%. calibre was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 1 topic tag (ebook), 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 | HRConvert2 | |
|---|---|---|
| GitHub stars | ★ 26K | ★ 1.4K |
| License | GPL-3.0 | GPL-3.0 |
| Written in | Python | PHP |
| Last push | 2026-09-17 | 2026-09-08 |
| Forks | ⑂ 2.7K | ⑂ 82 |
| 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 HRConvert2 if
- You want the HRConvert2 feature set and don't need the biggest community
- You prefer the GPL-3.0 license terms
- Your stack matches PHP
- You evaluated both and HRConvert2 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 HRConvert2
HRConvert2 is an open source, self hosted, resource aware file conversion server written in PHP and released under the GPL 3.0 license. It presents a public facing web workflow in which users drag, drop, convert, and download files without accounts, sessions, databases, cookies, or tracking. The project lives in the self hosted file conversion ecosystem, where it replaces hosted converters by running conversion tools on the operator's own machine.
read the full HRConvert2 overview →
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Frequently asked questions
Is calibre or HRConvert2 more popular?
calibre has 25,923 GitHub stars and HRConvert2 has 1,369. calibre has the larger community by that measure.
Are calibre and HRConvert2 free?
Both are open source. calibre is licensed under GPL-3.0 and HRConvert2 under GPL-3.0. Neither carries a licence fee.
What is the difference between calibre and HRConvert2?
calibre is written in Python and HRConvert2 in PHP. 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 HRConvert2?
Choose calibre if you want the larger community (25,923 stars) or its GPL-3.0 licence terms. Choose HRConvert2 if its feature set, stack or GPL-3.0 licence fits better. Both are self-hostable.