When comparing nomacs vs FastStone Image Viewer, the Slant community recommends FastStone Image Viewer for most people. In the question“What are the best image viewers for Windows?” FastStone Image Viewer is ranked 1st while nomacs is ranked 5th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Highly customizable
Pro Detailed view of image metadata
Pro Lots of image adjustment tools
Pro Simple and pleasant look
No cramped toolbars or large icons; the UI is cohesive, minimal and keeps out of your way.
Pro Lightweight
Starts very quickly and has a small memory footprint.
Pro You can work with hot keys that can be reassigned as you want them
Pro Frameless view
Pro Allows to cut (frame) images
It is important if you have to work with photos of documents and want to cut off the background on which you made photos.
Pro Flexible thumbnail views
Can display thumbnails in a strip or a zoomable grid as well, also has hotkey for both of these. Opening a folder is one of the main actions on the toolbar!
Pro Cross-platform
Has builds for Windows, Mac and Linux.
Pro Remembers last used folders
Often used folders (e.g., screenshots) can be quickly accessed.
Pro Batch image processing
Has tools for applying conversions etc. to many files at once.
Pro Can print to printer
Unlike most other image viewers.
Pro Supports new image formats out of the box
Such as WebP, AVIF, etc.
Pro Comparing two images
This feature is called Synchronization. With the synchronization it is possible that multiple viewers perform the same action (like panning, zooming, etc.). This feature is useful when comparing two images. See more here.
Pro Really fast
Pro Lots of features for simple editing
Pro Great for comparing and sorting multiple images
Pro Free
Pro Best keyboard controls
Pro Editing photo levels
Pro Built-in folder browser
Can browse folders, images and videos, all with thumbnails.
Pro Has dark mode
As well as Gray mode. Good for your eyes.
Cons
Con No support for JPEG-XL
Con Only partial support for HEIC
Apple's HEIC format is only partially supported. Nomacs can open individual images, but can't navigate among them.
Con Heavy compared to other Linux image viewers
Uses more memory and CPU than other lightweight image viewers. High CPU usage when starting.
Con Returns to default settings after update
Con Recent version has slowed down
The latest version (3.8) suddenly became very slow in Fedora 26. Slow to step from image to image; slow to open a directory; slow slow slow. Downgrading to the previous version (3.6) restored speed.
Con Free version is not valid for business usage
Only good for private use, small business licensing is very expensive.
Con Broken SVG Support
SVG images do not show at all.
Con Sometimes really sluggish
Showing the wait cursor for multiple seconds like executing large operations in the GUI thread.