XnView MP stands for Multi Platform = it is available for Windows, Linux and MacOS. It is a continuation of the older XnView Classic. In my opinion it is a great alternative to Windows photos app or any Linux image viewer that comes preinstalled. I even think it is an alternative to IrfanView. It is really fast and simple to use, supports more than 500 image formats, has built in folder browser, image converter, editor... AND MORE!
Smart Pix Manager - Smart Pix Manager is a powerful and reliable solution for the management and viewing of all documents, common images, sound (WMA, MP3), and video files (AVI, MPEG), etc.
IrfanView - IrfanView ... one of the most popular viewers worldwide.
JetPhoto Studio - JetPhoto Studio is a sleek and easy-to-use digital photo software that allows users to manage their photos in an attractive, intuitive mode and turning a sometimes frustrating chore into a fun and easy way by clicking only several steps.
FastStone Image Viewer - FastStone Image Viewer is a fast, stable, user-friendly image browser, converter and editor.
Photos on macOS - Photos keeps your images organized and accessible. Rediscover favorite shots with Memories. Access them on your devices with iCloud Photos.
JPEGView - JPEGView is a small and fast viewer/editor for JPEG, BMP, PNG, GIF and TIFF images.