nomacs is described as 'Free, open source image viewer, which supports multiple platforms. You can use it for viewing all common image formats including RAW and psd images' and is a very popular Image Viewer in the photos & graphics category. There are more than 50 alternatives to nomacs for a variety of platforms, including Windows, Linux, Mac, Flathub and Xfce apps. The best nomacs alternative is IrfanView. It's not free, so if you're looking for a free alternative, you could try IrfanView or XnView MP. Other great apps like nomacs are XnView Classic, FastStone Image Viewer, qView and Gwenview.
Compact and efficient image application offering viewing, editing, and conversion with batch processing, multi-language support, plugin extensibility, and ad-free operation suitable for Windows and portable use.
Comprehensive photo management software for viewing, batch converting, editing and resizing images and creating thumbnail sheets.
A feature-rich, simple-to-use app seamlessly integrated with a clean, minimal and modern user interface.
XnView Classic is an efficient image viewer, browser and converter for Windows with built-in support for over 500 image formats.
Fast image browser and editor for Windows with robust support for browsing, editing, and conversion. Features red-eye removal, resizing, enhanced EXIF access, and musical slideshows with over 150 effects.
Fast and lightweight Qt-based image viewer with support for Windows, macOS, and Linux. Features include multiple format support, customizable interface, GIF playback, high-resolution display compatibility, and efficient navigation through keyboard shortcuts.
Offers quick browsing and display of various image formats, basic editing tools like crop, rotate, lossless JPEG manipulation, folder browsing as thumbnails or slideshows, supports XCF, drag-and-drop, metadata viewing, KDE integration, and plugin extensions.
Many functions, able to show multiples images, easy save image...
Lightweight Simple Image Viewer with Slide show feature, Resize and Lossless-cut, Color correction, Rename, Multi-language and more...
PicView is a fast, free and fully customizable picture viewer for macOS and Windows 10/11. It supports virtually all image file types, including (animated) WEBP, (animated) GIF, SVG, AVIF, HEIC, PSD and many others.
Qt5 image viewer with optional video support. Ability to quickly copy / move images to different folders. Can open some extra formats (JPEG-XL, AVIF, APNG, HEIF/HEIC, RAW) via third-party image plugins.
Video playback, better UI and grid layout and can move, cut, copy & paste files.
Offers organization, viewing, and editing tools for digital images, supports over 700 RAW formats, enables metadata embedding and syncing, dynamic category and keyword filters, workflow optimizations, non-destructive edits, detailed image preview, and sharing options.
Desktop app for photo sorting on Windows & Mac, managing JPG+RAW files. Sort photos into folders using keys, providing easy navigation and clean interface without deletion, ensuring a focused experience with flexible viewing, safe storage, and no fluff.
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XNview-MP (not listed) might be a good alternative. And it's multi-platform... I do use it, it has a lot of features, but is not small or simple.