Next to Adobe Acrobat Reader (64-bit) or Foxit PDF Reader, SumatraPDF is a much smaller tool with a narrower aim: open documents and books quickly. Version 3.6.1 is a free Windows program of 10.6 MB, filed under PDF readers. Besides PDF it opens EPUB, MOBI, CBZ, CBR, FB2, CHM, XPS and DjVu files, so one viewer can cover manuals, ebooks and comics.
Krzysztof Kowalczyk and an open GPL-3.0 codebase
SumatraPDF is developed by Krzysztof Kowalczyk, and the project publishes its source code on GitHub at sumatrapdfreader/sumatrapdf. The license is GPL-3.0, and the app is free.
The developer says simplicity of the interface is a priority.
Nine formats in one small viewer
The reader handles PDF, EPUB, MOBI, CBZ, CBR, FB2, CHM, XPS and DjVu files. It also views images. That covers ebooks, comic archives and older document formats without separate programs.
The developer says it is small and starts up fast. It has no editing features, even though the app also appears in our best free PDF editors group.
Windows requirements and where it fits
SumatraPDF is a Windows app with the package ID SumatraPDF.SumatraPDF.
If you want a different feature set, alternatives include Foxit PDF Reader, PDF-XChange Editor, PDF24 Creator, PDFgear and Xodo PDF Reader.
What's new in 3.6.1
Version 3.6.1 came out on April 6, 2026.
SumatraPDF pros and cons
Pros
- Free, with a GPL-3.0 license
- Opens PDF, EPUB, MOBI, CBZ, CBR, FB2, CHM, XPS and DjVu
- Download is only 10.6 MB
- Source code is public on GitHub
- Developer states it starts up fast
Cons
- Windows only
- No editing features
- No portable build or minimum Windows version is listed
Is SumatraPDF safe?
Krzysztof Kowalczyk publishes SumatraPDF, and the full source sits on GitHub under the GPL-3.0 license. Anyone curious about what a PDF, EPUB or comic reader does with their files can read the code, or build the program from source and compare it with the released version.
How to install SumatraPDF
- Press the download button to get the official file.
- Run the installer you saved and confirm the Windows security prompt if the publisher matches.
- Follow the setup steps, then start SumatraPDF from the Start menu.
