digiKam - Professional Photo Management with the Power of Open Source
ACDSee - ACDSee is an image viewer that uses very little system resources, and it has a small, sleek size that won't take up much space on your system.
Photos on macOS - Photos keeps your images organized and accessible. Rediscover favorite shots with Memories. Access them on your devices with iCloud Photos.
XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!
Flickr - image and video hosting website
Capture One - Capture One is an all-in-one photo-editing software that comes with all powerful tools to make your photo editing smoother and more precise than ever.