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WonderPen vs Hammer: catalog facts
WonderPen	Hammer
Paid Proprietary software sold through a purchase page on the developer's site.	Free Free and open source under the MIT licence.
Windows, macOS, Linux	Windows, Linux, Android
Unlimited-depth tree for chapters and documents Export to PDF, Word, EPUB and web pages, including whole books	Native apps rather than a web page in a wrapper Runs on phones and desktops
Proprietary and paid Cloud sync relies on the developer's own service	Issue reporting is steered towards Discord Feature details are sparse in the available documentation
Downloadable app	Downloadable app
Closed source	Open source
License: Proprietary	License: MIT
Not stated if an account is needed	Not stated if an account is needed
Works offline	Not stated if it works offline
Official website Full listing and sources Checked October 1, 2026	Official website Full listing and sources Checked October 2, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.