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Readest vs Librum: catalog facts
Readest	Librum
Freemium The app is free and open source under the AGPL. The optional cloud sync service has paid…	Free Free and open source.
Windows, macOS, Linux, Android, Web, iOS	Windows, macOS, Linux
Reads EPUB, PDF, MOBI, AZW3, FB2, CBZ, TXT and Markdown in one app The same reader on macOS, Windows, Linux, Android, iOS and the web	Reader and library manager in one app Runs on several desktop platforms
Cloud sync is a hosted service with paid tiers, not purely local A young project, so features and stability are still moving	Sync depends on the project's service Smaller project than established readers like Calibre
Downloadable app, Web application	Downloadable app
Open source	Open source
License: AGPL-3.0	License: GPL-3.0
No account needed	Not stated if an account is needed
Works offline	Not stated if it works offline
Official website Full listing and sources Checked September 21, 2026	Official website Full listing and sources Checked October 2, 2026

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