ICNS (Mac OS X Icon Resource File)

The ICNS System file format

Icon files used on Mac computers and other OS X devices use the file extension ICNS. These icon files are used to display a small image (icon) in the OSX Finder or dock, representative for an application which it is linked to. ICNS files support images in a variety of dimensions. They range from 16x16 pixels to 512x512 pixels. As of OS X Mountain Lion, ICNS files can support even bigger images, namely the 1024x1024 pixels dimension.

Technical details of ICNS files

The content of the ICNS file typically consists of one or more images in the PNG format. This format is pretty handy as a base for the ICNS since it allows transparency. The ICNS file supports 1-bit as well as 8-bit alpha channels. What differentiates them from Windows' ICO files is that ICNS files can contain individual icon resources, thus acting more like a container file.

More information about the ICNS file format

File extension .icns
File category System
Associated programs Adobe Photoshop with IconBuilder for Mac Plugin (Mac)
Apple Preview (Mac)
Axialis IconWorkshop (Windows)
Folder Icon X (Mac)
Icon Machine (Mac)
Iconographer (Mac)
Inkscape (Windows, Mac & Linux)
Snap Converter (Mac)
XnViewMP (Windows, Mac & Linux)
Useful links Further Information About The Apple ICNS File
Developer Apple