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SioyekSumatra PDF
Free

Free and open source under the GPL. The developer accepts optional donations.

 Free

Completely free and open source with no ads, bundled software or subscription. No account…

Windows, macOS, Linux Windows, Command line
  • Opens a referenced figure, table or citation in an overlay without losing your place
  • Searchable highlights, bookmarks and marks across your whole library
  • 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 last tagged release is from December 2022
  • macOS shows a quarantine warning that needs working around on first launch
  • 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

Checked September 21, 2026

Checked September 20, 2026

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