ICNS (often written in lowercase as icns) is the native icon format of Mac OS and OS X.
It goes by many other names, including Apple Icon, Macintosh Icon, Mac OS Icon, Macintosh OS X Icon, Mac OS X Icon Resource, Mac OS icns Resource, and IconFamily Resource.
There are usually multiple images in a file. Supported image sizes are 16×12, and 16, 32, 48, 128, 256, 512, and 1024 pixels square.
Files begin with ASCII characters "