# nomacs/nomacs

nomacs is a free image viewer for windows, linux, and mac systems.

Repository: https://github.com/nomacs/nomacs
Canonical: https://ross.abutalabs.com/products/nomacs
Homepage: https://nomacs.org/
Language: C++
License: GPL-3.0
License Family: copyleft
Topics: nomacs, image-viewer, picture-viewer, photo-editor, opencv, avif, jpeg-xl, jpegxl
Last push: 2026-08-26T20:53:54+00:00

## Health v2 (maintenance only)
Score: 91/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 99, release rhythm 75, longevity 100
- inputs: {"age_days": 4746, "days_push": 7, "days_rel": 7, "gap_med": 119.5, "n_releases_24m": 3}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 3135, forks 200 (observed 2026-08-28T04:07:45.639181+00:00)

## What it is
nomacs is a free, open-source image viewer for Windows, Linux, macOS, FreeBSD, and other platforms, built with Qt and optionally OpenCV. It supports common image formats including RAW and PSD, offers basic editing, metadata display, thumbnails, and synchronized multi-instance viewing for image comparison.

## Use cases
- view raw camera files like cr2 and nef
- open psd and avif images on linux
- compare two images side by side with synced zoom and pan
- browse a folder of photos with thumbnails and filters
- adjust brightness, contrast, and color of a photo
- view image metadata and histograms
- view images inside zip archives

## When to choose
- you need a fast, free image viewer across Windows, Linux, and macOS
- you need RAW, PSD, AVIF, HEIF, or JPEG XL support
- you want to compare images via synchronized viewers
- you prefer open-source software free for commercial use

## When to avoid
- you need advanced photo editing like layers or retouching
- you need a lightweight CLI-only tool
- you require non-GPL licensing for redistribution

## Facets
- artifact type: application
- maturity: stable
- function: image-processing, gui
- domain: image-processing, photography, cross-platform, desktop-applications
- platform: windows, cross-platform
- tags: image-viewer, raw-images, psd, avif, jpeg-xl, qt, metadata, viewer-synchronization, thumbnails, photo-editor, linux, macos, desktop

## Member repositories
- nomacs/nomacs (main) score 91

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:07:45.639181+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-29T18:45:37.050565+00:00, confidence not recorded.
  - readme: https://github.com/nomacs/nomacs (fetched 2026-08-28T04:07:45.639181+00:00, sha 48584001aeab)
  - homepage: https://nomacs.org/ (fetched 2026-08-29T09:40:53.039113+00:00, sha 3dbc8151c1b7)
  - site_page: https://nomacs.org/docs/getting-started/introduction (fetched 2026-08-29T09:40:53.047803+00:00, sha 6c5293d21271)
  - site_page: https://nomacs.org/docs/documentation/features (fetched 2026-08-29T09:40:53.049695+00:00, sha 2bbebd387074)
  - site_page: https://nomacs.org/docs/contributing/code-of-conduct (fetched 2026-08-29T09:40:53.051551+00:00, sha 5264f53bd8b8)
- Data as of 2026-08-30T08:39:29.467469+00:00.