Compare software

Chaka Book Reader vs Orion Viewer: catalog facts
Chaka Book Reader	Orion Viewer
Free Free and open source under AGPL-3.0-or-later.	Free Free and open source under the GPL.
Android	Android
Opens a very wide range of document and comic formats Reads files directly from archives	Opens DjVu as well as PDF, XPS, CBZ and TIFF Configurable tap zones and key bindings for page turning
Android only No release downloads listed on the repository	Viewer only, with no PDF editing Interface is functional rather than polished
Downloadable app	Downloadable app
Open source	Open source
License: AGPL-3.0	License: GPL-3.0-or-later
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 October 2, 2026

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