Nomacs is a free, open source image viewer, which supports multiple platforms. Developed by Markus Diem, Stefan Fiel and Florian Kleber
License: Open Source
FastStone Image Viewer is a powerful and user-friendly tool with extensive image editing features and format support, primarily for Windows users. In contrast, Nomacs is a lightweight, open-source alternative that excels in color management and multi-platform support but lacks some of the advanced editing capabilities of FastStone.