nomacs is a free, open source image viewer, which supports multiple platforms. You can use it for viewing all common image formats including RAW and psd images.

nomacs features semi-transparent widgets that display additional information such as thumbnails, metadata or histogram. It is able to browse images in zip or MS Office files which can be extracted to a directory. Metadata stored with the image can be displayed and you can add notes to images. A thumbnail preview of the current folder is included as well as a file explorer panel which allows switching between folders. Within a directory you can apply a file filter, so that only images are displayed whose filenames have a certain string or match a regular expression. Activating the cache allows for instantly switching between images.

nomacs includes image manipulation methods for adjusting brightness, contrast, saturation, hue, gamma, exposure. It has a pseudo color function which allows creating false color images. A unique feature of nomacs is the synchronization of multiple instances. With this feature you can easily compare images by zooming and/or panning at the exactly same position or even by overlaying them with different opacity.
nomacs is licensed under the GNU General Public License v3 and available for Windows, Linux, FreeBSD, Mac, and OS/2. It is free for private and commercial use. If you want to report any bugs or request new features please use our tracker.