Filename extension .icns Uniform Type Identifier (UTI) com.apple.icns Type of format icon file format | Type code icns Developed by Apple Inc. | |
The Apple Icon Image format is the icon format used in Apple Inc.'s macOS. It supports icons of 16 × 16, 32 × 32, 48 × 48, 128 × 128, 256 × 256, 512 × 512, and 1024 × 1024 pixels, with both 1- and 8-bit alpha channels and multiple image states (example: open and closed folders). The fixed-size icons can be scaled by the operating system and displayed at any intermediate size.
Contents
File structure
The file format consists of an 8 byte header, followed by any number of icons.
Compression
Over time the format has been improved and there is support for compression of some parts of the pixel data. The 32-bit ("is32", "il32", "ih32","it32") pixel data is often compressed (per channel) with a format similar to PackBits.
Some sources mentioned that the OS supports both compressed or uncompressed data chunks.
Icon types
Support
Various image viewers can load *.icns files, a free and open source converter from or to PNG also exists. GTK+ can load *.icns resources since 2007. Other tools supporting the format include the Apple Icon Composer and icns Browser, The Iconfactory, and IconBuilder.