Preview is described as 'Native macOS tool for viewing, annotating, and editing images and PDFs, offers cropping, resizing, markup tools, page rearrangement, and export to multiple formats' and is a very popular Image Viewer in the photos & graphics category. There are more than 100 alternatives to Preview for a variety of platforms, including Windows, Mac, Linux, Android and iPhone apps. The best Preview alternative is SumatraPDF, which is both free and Open Source. Other great apps like Preview are Okular, IrfanView, XnView MP and ImageGlass.
Fragment is an image viewer with cool features like: Upload and Share, HUD User Interface, Peeking and Skimming, Animated GIFs, History, Thumbnails, Fill View and it is fast!
Features:
Pixea is an image viewer for macOS with a nice minimal modern user interface. Pixea works great with JPEG, HEIC, PSD, RAW, WEBP, PNG, GIF, and many other formats.
sxiv is a simple image viewer for X. It only has the most basic features required for fast image viewing.
Shelf is a convergent document viewer that supports PDF and EPUB files. With Shelf, you can organize your document collection by creating tags, like other Maui applications.
Mexico
PhotoPad picture editor is the fastest and most fun way to edit your digital photos. PhotoPad is one of the most stable, easy-to-use, and comprehensive photo editors available.
Australia
In version 8, Google Chrome introduced a free PDF viewer, installed by default. While this plug-in lacks many features of the Adobe Acrobat Plug-in, it is much faster and lighter, and updates with the browser rather than an external utility.
United States
The simplest PDF viewer. Safe (doesn't require permissions), lightweight (just 6,9MB) and modern.
Italy
EU
Apowersoft PDF Converter is a one-stop PDF tool, which not only contains tools to converting PDF file to other formats, but can also convert other formats to PDF, even more, it can merge PDF, split PDF, extract images, OCR, encrypt/decrypt PDF, etc.
DocInspector is a professional, offline-first document processing and privacy-auditing application designed for legal, financial, and corporate teams. It enables users to clean, repair, and bundle large volumes of documents locally without relying on cloud services.
Moldova
Ashampoo PDF Free is a software for opening, reading, and creating PDF files. It includes a built-in printer driver for generating PDFs from any Windows application, a compact and fast PDF reader, and the ability to fill out interactive and static forms.
GermanyEU
United Kingdom
Deli PDF Converter is a Windows PDF converter software capable of converting PDF documents to various file formats, such as PDF to Word, PDF to image, PDF to Html, PDF to Flash, etc., besides, it can turn other file formats to PDF document.
China
