XnView MP is recommended for photographers, graphic designers, and anyone who needs to organize, view, and edit a large collection of images. It's also well-suited for users who require bulk processing and conversion of image files.
PicPick is recommended for anyone who needs a powerful and easy-to-use screen capturing and image editing solution. This includes teachers preparing instructional materials, web developers needing to capture and annotate screenshots for feedback, graphic designers who require quick image touch-ups, and anyone in need of a feature-rich yet simple screen capture tool.
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!
IrfanView - IrfanView ... one of the most popular viewers worldwide.
ShareX - ShareX is a free and open source program that lets you capture or record any area of your screen...
FastStone Image Viewer - FastStone Image Viewer is a fast, stable, user-friendly image browser, converter and editor.
Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.
JPEGView - JPEGView is a small and fast viewer/editor for JPEG, BMP, PNG, GIF and TIFF images.
LightShot - The fastest way to take a customizable screenshot.