nomacs

nomacs is a desktop image viewer with tools for browsing, inspecting, adjusting, and comparing images. It is a strong fit for image-processing users who need to review files or compare processing stages; it is not a substitute for a full image editor.

Overview

Founded in 2011, nomacs is free for private and commercial use under the GNU General Public License v3. Its comparison tools give it a more focused role than a basic viewer, while its adjustment controls are best treated as quick corrections rather than a complete editing workflow.

It supports common image formats, including RAW and PSD, but format support can depend on Qt image plugins, KImageFormats, and optional build features. That makes it sensible to confirm support for any format central to your work before choosing a build.

Key features

Browse and inspect

Semi-transparent widgets can display thumbnails, metadata, and histograms, and users can add notes to images. Folder thumbnail previews and filename filters using text or regular expressions help with collection review. Browsing images inside ZIP or MS Office files is useful when images arrive bundled in archives or documents.

Make quick adjustments

Brightness, contrast, saturation, hue, gamma, and exposure controls cover common tonal and color changes. Pseudo-color rendering can show false-color images. These options make nomacs more useful than a read-only viewer, but they do not position it as a full image-editing suite.

Compare images

Multiple nomacs instances can synchronize panning and zooming, and images can be overlaid at different opacity levels. That is particularly useful for comparing processing stages or inspecting differences while keeping views aligned. Readers who need more extensive editing should look elsewhere.

Pricing

The nomacs plan costs nothing, with no free trial because the software is free. The GNU General Public License v3 permits private and commercial use, so there is no paid tier to unlock those use cases.

Platforms

nomacs supports Windows, Linux, macOS, FreeBSD, and OS/2. Downloads include Windows 64-bit installer and portable packages, Linux packages plus Flatpak and AppImage, and macOS arm64 and x86_64 builds. Windows XP and Vista are not supported in development since version 3.0; version 2.4.6 can be used on those systems.

Who it's for

Choose nomacs if you want a free viewer that can inspect metadata and histograms, browse image collections, make modest adjustments, and compare processing stages. Its synchronized views and opacity overlays are the clearest reason to choose it over a simple viewer. It is a weaker fit if you need a full editing suite or rely on a specific image format without first checking the build's support.

Pros and cons

• Pros: Free for private and commercial use under GPLv3, with no paid plan required.
• Pros: Synchronized panning and zooming plus opacity overlays support direct image comparison.
• Pros: Metadata, histograms, notes, collection filters, and archive or document browsing combine several review tasks in one viewer.
• Cons: Format support varies with plugins and build options, which can complicate workflows dependent on a particular format.
• Cons: Adjustment controls are basic, so users seeking a full editor should choose another kind of tool.

Alternatives

ImageGlass is another free-plan option for Windows, Linux, and macOS, with a free trial; choose it if that alternative better suits your viewer needs. XnConvert offers free use for private, educational, and non-profit use, while its company license is 6.50 EUR; consider it if those terms fit your intended use. Geeqie is a free, GPLv2 option across Windows, Linux, and macOS. Pineapple Pictures has a free MIT-licensed viewer, with a paid itch.io purchase offering experimental additional format support. qView is a free, open-source GPLv3 alternative across Windows, Linux, and macOS. ApolloOne is a macOS-only choice with a free version indefinitely and a purchase reminder after 14 days, as well as a $14.99 a year Standard subscription. FastStone Image Viewer is Windows-only, with free personal and educational use and a $34.95 a month commercial lifetime license. GNOME Remote Desktop is a free Linux and self-hosted option focused on remote desktop rather than image viewing.

Browse more options in Photo Viewer Software or File Viewer Software.

Verdict

nomacs is an easy recommendation for image reviewers who want comparison tools, basic adjustments, and broad desktop platform coverage without a usage fee. Its main limitation is the combination of modest editing depth and build-dependent format support; choose a more specialized tool if either is essential to your work.