What Is nomacs? A Free, Open-Source Image Viewer

Updated

nomacs is a free, open-source image viewer that runs on multiple platforms. It handles all common image formats, including RAW and PSD files, and adds editing and multi-viewer comparison on top of basic viewing. It is licensed under the GNU General Public License v3.0, so you can use, inspect, and redistribute it under those terms. If you need a no-cost viewer for everyday formats plus camera RAW and Photoshop files, nomacs is built for that job.

What nomacs does

The project describes three core capabilities:

  • Image viewing — opens the most common image formats, including RAW.
  • Image editing — supports cropping, resizing, rotating, color adjustments, and more.
  • Viewer synchronization — the same action (panning, zooming, and similar) can be applied across multiple viewers at once, which makes comparing two images straightforward.

The synchronization feature is the least common of the three in typical viewers. Instead of nudging two windows to the same position by hand, you act on one and the others follow, so side-by-side comparison stays aligned.

Who it fits

Your situation nomacs as a fit
You want a free, open-source viewer Yes — GPL v3.0
You work across operating systems Yes — multiple platforms supported
You open RAW or PSD files Yes — both are listed as supported
You need light edits (crop, resize, rotate, color) Yes — built in
You compare two images closely Yes — viewer synchronization
You need a full photo editor or RAW development suite Probably not — editing here is basic

How to get it

The site links to GitHub, where the current release is listed as v3.22.0. Download from the project's GitHub page, install for your platform, and open an image to confirm it renders. Then test the two features that distinguish it: open a second image and try synchronized panning or zooming, and run a crop or color adjustment to see whether the built-in editing covers your needs.

Common points to check before committing

  • Format coverage in practice — the site says "most common" formats plus RAW and PSD; if you rely on an unusual format, verify it opens before making nomacs your default.
  • Editing depth — cropping, resizing, rotating, and color adjustments are listed, but this is a viewer with editing tools, not a replacement for a dedicated editor.
  • Licensing terms — GPL v3.0 governs use and redistribution; read it if you plan to bundle or modify the software.

For straightforward viewing, format breadth, and quick side-by-side comparison, nomacs covers the ground. For heavy editing or RAW development, treat it as a viewer that also does the basics.