Compare software

Calibre vs Sumatra PDF: catalog facts
Calibre	Sumatra PDF
Free Free and open source, funded by donations.	Free Completely free and open source with no ads, bundled software or subscription. No account…
Windows, macOS, Linux	Windows, Command line
Converts between all the major ebook formats, including for Kindle Fetches metadata and covers from the internet automatically	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
The interface is dense and has accumulated two decades of features It will not remove DRM; that requires third-party plug-ins with their own legal questions	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
Downloadable app	Downloadable app
Open source	Open source
License: GPL-3.0	License: GPL-3.0
No account needed	Not stated if an account is needed
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 20, 2026

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