head to head · open source
calibre vs WritingTools
calibre has 25,953 GitHub stars, 2,697 forks, 6 open issues and last shipped today. WritingTools has 2,455 stars, 159 forks, 79 open issues and last shipped 1 months ago. calibre leads on adoption by 957% (25,953 vs 2,455 stars). calibre is written in Python under GPL-3.0; WritingTools is written in Swift under GPL-3.0. calibre has attracted 10% as many forks as stars, WritingTools 6%. calibre 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
| calibre | WritingTools | |
|---|---|---|
| GitHub stars | ★ 26K | ★ 2.5K |
| License | GPL-3.0 | GPL-3.0 |
| Written in | Python | Swift |
| Last push | 2026-09-20 | 2026-08-19 |
| Forks | ⑂ 2.7K | ⑂ 159 |
| 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 WritingTools if
- You want the WritingTools feature set and don't need the biggest community
- You prefer the GPL-3.0 license terms
- Your stack matches Swift
- You evaluated both and WritingTools 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 WritingTools
WritingTools is an open source, system wide writing assistant for Windows, Linux, and macOS. It is inspired by Apple Intelligence Writing Tools and uses cloud based or local large language models to proofread, rewrite, summarize, and transform selected text across applications. The project is written in Swift and released under the GPL 3.0 license. The README states it works in nearly any language.
read the full WritingTools overview →
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Frequently asked questions
Is calibre or WritingTools more popular?
calibre has 25,953 GitHub stars and WritingTools has 2,455. calibre has the larger community by that measure.
Are calibre and WritingTools free?
Both are open source. calibre is licensed under GPL-3.0 and WritingTools under GPL-3.0. Neither carries a licence fee.
What is the difference between calibre and WritingTools?
calibre is written in Python and WritingTools in Swift. 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 WritingTools?
Choose calibre if you want the larger community (25,953 stars) or its GPL-3.0 licence terms. Choose WritingTools if its feature set, stack or GPL-3.0 licence fits better. Both are self-hostable.