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Librum vs Calibre: catalog facts
Librum	Calibre
Free Free and open source.	Free Free and open source, funded by donations.
Windows, macOS, Linux	Windows, macOS, Linux
Reader and library manager in one app Runs on several desktop platforms	Converts between all the major ebook formats, including for Kindle Fetches metadata and covers from the internet automatically
Sync depends on the project's service Smaller project than established readers like Calibre	The interface is dense and has accumulated two decades of features It will not remove DRM; that requires third-party plug-ins with their own legal questions
Downloadable app	Downloadable app
Open source	Open source
License: GPL-3.0	License: GPL-3.0
Not stated if an account is needed	No account needed
Not stated if it works offline	Works offline
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked September 20, 2026

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