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FBReader vs Thorium Reader: catalog facts
FBReader	Thorium Reader
Freemium The reader is free. Some format plugins and premium features are paid.	Free The open-source software is available without a license fee. Hosting, hardware and…
Windows, macOS, Linux, Android, iOS	Windows, macOS, Linux
Same library and reading position across desktop and mobile Reads custom OPDS catalogues as well as local files	Supports library imports, bookmarks and adjustable reading layouts.
Some features and formats need paid add-ons The desktop builds lag the mobile apps	Format and protection support depend on the book being opened.
Downloadable app	Downloadable app
Closed source	Open source
License not stated	License: BSD-3-Clause
Not stated if an account is needed	Not stated if an account is needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Checked September 22, 2026	Official website Full listing and sources Checked September 22, 2026

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