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Orion Viewer vs Librera Reader: catalog facts
Orion Viewer	Librera Reader
Free Free and open source under the GPL.	Free Free to download.
Android	Android
Opens DjVu as well as PDF, XPS, CBZ and TIFF Configurable tap zones and key bindings for page turning	Wide format support including DjVu and comics Auto-scan of book folders with reading progress
Viewer only, with no PDF editing Interface is functional rather than polished	Android only Many settings can take time to learn
Downloadable app	Downloadable app
Open source	Open source
License: GPL-3.0-or-later	License: GPL-3.0
No account needed	No account needed
Works offline	Works offline
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked September 23, 2026

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