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Secure PDF Viewer vs Librera Reader: catalog facts
Secure PDF Viewer	Librera Reader
Free Free and open source under the MIT and Apache-2.0 licenses.	Free Free to download.
Android	Android
Requires no app permissions Uses a sandboxed WebView to display PDF streams	Wide format support including DjVu and comics Auto-scan of book folders with reading progress
Android only	Android only Many settings can take time to learn
Downloadable app	Downloadable app
Open source	Open source
License: MIT AND Apache-2.0	License: GPL-3.0
Not stated if an account is needed	No account needed
Not stated if it works offline	Works offline
Official website Full listing and sources Checked October 8, 2026	Official website Full listing and sources Checked September 23, 2026

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