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Sumatra PDF vs Okular: catalog facts
Sumatra PDF	Okular
Free Completely free and open source with no ads, bundled software or subscription. No account…	Free Free and open source under the GPL.
Windows, Command line	Windows, macOS, Linux
Opens PDF, EPUB, MOBI, FictionBook, CBZ/CBR/CBT/CB7, DjVu, XPS, CHM, SVG and many image formats including HEIC and AVIF Lightweight and fast; the portable single .exe build writes nothing to the registry	One viewer for a very wide range of document and comic formats Annotations are stored separately, so the original file is untouched
Windows only (Windows 7 through 11; XP and Vista need version 3.1.2); no macOS or Linux version Only unencrypted EPUB and MOBI/AZW ebooks open; DRM-protected files are not supported	Pulls in KDE libraries on non-KDE desktops It is a viewer and annotator, not a PDF editor
Downloadable app	Downloadable app
Open source	Open source
License: GPL-3.0	License: GPL-2.0
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 20, 2026	Official website Full listing and sources Checked September 22, 2026

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