Best Open-Source PDF Readers 2026: 7 Options Compared

A PDF reader should open files fast and stay out of the way, and the open-source field gives you several philosophies. SumatraPDF is a light Windows reader that starts almost instantly. Okular, from KDE, adds annotations and form filling, and Evince is the GNOME default with a clean interface. Zathura and MuPDF are minimalist viewers driven from the keyboard, popular with Linux power users. Sioyek was designed for textbooks and research papers, with features for jumping between references. PDF.js is the viewer Firefox uses and also a JavaScript library you can embed in your own website. Choose SumatraPDF on Windows, Okular or Evince on Linux, and Sioyek if you read dense papers all day. Zathura and MuPDF suit people who prefer shortcuts to menus. The trade-off is feature depth: free readers handle viewing and light markup, but rarely include the signing, redaction or document-comparison tools that paid readers bundle. MuPDF is licensed under AGPL-3.0, which matters if you plan to embed it in a product, so read the terms before shipping. Licences below come from the projects' repositories or official pages as of the check date, and no performance benchmarks were run.

SumatraPDF

Light Windows reader that is open source and free to use. Stays focused on viewing, with little annotation support.

Price: Free (Free with no ads, bundled software or subscription; a portable version runs without installing) (SumatraPDF pricing, checked 2026-10-23).

Platforms and license: Windows. Open source (license not named on the page) (open source) (license source).

Project activity: 17.9k GitHub stars · latest release 3.6.1rel (Apr 6, 2026) · last commit Oct 28, 2026

Best for: Fast reading on Windows.

Worth knowing: Windows only (7 to 11, 32-bit, 64-bit and ARM64). Reads PDF, EPUB, MOBI, CBZ, CBR, DjVu, XPS, CHM and images. No paid tier mentioned.

Okular

GPLv2+ KDE viewer with annotation and form-filling features. Heavier than minimal readers, but a good all-purpose Linux choice.

Price: Free (Free software; no paid tier) (Okular pricing, checked 2026-10-23).

Platforms and license: Linux, Windows (Microsoft Store), macOS (nightly builds only). GPLv2+ (open source) (license source).

Best for: Annotating on Linux.

Evince

GPL-2.0 document viewer for the GNOME desktop. Simple and reliable, with fewer markup tools than Okular.

Price: Free (Free and open source document viewer) (Evince pricing, checked 2026-10-24).

Platforms and license: Desktop (GNOME). GPL-2.0 (open source) (license source).

Project activity: 377 GitHub stars · last commit Oct 12, 2026

Best for: GNOME desktops.

Worth knowing: GitHub repository is a read-only mirror of the GNOME GitLab project. License taken from the repository metadata and LICENSE file; description from the project README. No paid plan was checked.

Sioyek

GPL-3.0 PDF viewer designed for textbooks and research papers, with a keyboard-driven workflow aimed at people reading dense material all day.

Price: Free (Free and open source PDF viewer) (Sioyek pricing, checked 2026-10-24).

Platforms and license: Desktop. GPL-3.0 (open source) (license source).

Project activity: 10k GitHub stars · latest release v2.0.0 (Dec 16, 2022) · last commit Oct 22, 2026

Best for: Researchers and students.

Worth knowing: README: a PDF viewer with a focus on textbooks and research papers. License taken from the repository metadata and LICENSE file; description from the project README. No paid plan was checked.

zathura

Zlib-licensed document viewer driven from the keyboard, popular with Linux power users. Plugins add formats.

Price: Free (Free and open source document viewer) (zathura pricing, checked 2026-10-24).

Platforms and license: Desktop (Unix-like). Zlib (open source) (license source).

Project activity: 3.4k GitHub stars · last commit Oct 27, 2026

Best for: Keyboard-centric setups.

Worth knowing: License taken from the repository metadata and LICENSE file; description from the project README. No paid plan was checked.

MuPDF

AGPL-3.0 lightweight renderer and viewer from Artifex. AGPL terms apply if you embed it in your own product.

Price: Free (Free under AGPL-3.0) (MuPDF pricing, checked 2026-10-24).

Platforms and license: Desktop, Library. AGPL-3.0 (open source) (license source).

Project activity: 3k GitHub stars · last commit Oct 27, 2026

Best for: Small footprint and embedding.

PDF.js

Apache-2.0 HTML5 PDF viewer from Mozilla, usable as a library on your own web pages.

Price: Free (Free and open source PDF viewer built with HTML5) (PDF.js pricing, checked 2026-10-24).

Platforms and license: Web browser, JavaScript library. Apache-2.0 (open source) (license source).

Project activity: 54.1k GitHub stars · latest release v6.4.299 (Oct 3, 2026) · last commit Oct 27, 2026

Best for: Showing PDFs in a website.

Worth knowing: README: viewer built with HTML5. License taken from the repository metadata and LICENSE file; description from the project README. No paid plan was checked.

Which one to pick

• You use Windows and want the lightest reader: SumatraPDF
• You read research papers and jump between references: Sioyek
• You mark up PDFs on Linux: Okular
• You need to show PDFs inside a web page: PDF.js