Mozilla PDF.js vs qView

Mozilla PDF.js is a free, web standards-based platform for parsing and rendering PDF files. Developers can use its display API to render documents and retrieve information, or adapt the viewer layer for a custom interface. That viewer is used in Firefox and project browser extensions. PDF.js renders annotations and supports adding a subset of annotation types, and it supports form filling; OCR is not provided. The project targets HTML5-compliant browsers and includes a legacy build for older browsers, although PDF feature support varies by browser and version. Prebuilt builds are available, with hosted copies listed through jsDelivr, cdnjs, and unpkg. Developers can clone and build it locally, but some browsers require a local web server instead of opening PDFs through file URLs. Cross-origin requests are blocked by default, so CORS or a server proxy may be needed. For large documents, rendering only visible pages can reduce memory use. PDF.js is licensed under Apache 2.0.

qView is a free, open-source image viewer designed to keep the image prominent, with a title bar and no toolbar clutter. It supports common formats including BMP, GIF, JPG, PNG, TIFF, and WebP, as well as RAW images and color management. For browsing, it includes animated GIF controls, file history, rotation, mirroring, and multithreaded preloading. Preferences are configurable. The maker describes qView as quick to open and light on memory and CPU. It is based on Qt5 and licensed under GPLv3, with a listed price of free. Windows downloads include 64-bit installer, 32-bit, and standalone options; the installer requires Visual C++ 2015 or later. macOS options include a DMG for macOS 12 or later, a legacy download for macOS 10.13 or later, and Homebrew. Linux choices include distribution packages, AppImage, Flatpak, and a source tarball. The download page also links to bug reporting, Discord, translation contributions, and nightly builds.