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Thorium ReaderCalibre
Free

The open-source software is available without a license fee. Hosting, hardware and…

 Free

Free and open source, funded by donations.

Windows, macOS, Linux Windows, macOS, Linux
  • Supports library imports, bookmarks and adjustable reading layouts.
  • Converts between all the major ebook formats, including for Kindle
  • Fetches metadata and covers from the internet automatically
  • Format and protection support depend on the book being opened.
  • 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: BSD-3-Clause License: GPL-3.0
Not stated if an account is needed No account needed
Not stated if it works offline Works offline

Checked September 22, 2026

Checked September 20, 2026

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