Apple Icon Image format

Apple Icon ImageFilename extension .icnsInternet media typeimage/x-icnsType codeicnsUniform Type Identifier (UTI)com.apple.icnsMagic number69 63 6e 73Developed byApple Inc.Type of formatIcon file format The Apple Icon Image format (.icns) is an icon format used in Apple Inc.'s macOS. It supports icons of 16 × 16, 32 × 32, 48 × 48, 128 × 128, 256 × 256, 512 × 512 points at 1x and 2x scale, 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. As of macOS 11, asset catalogs are the preferred file format for macOS custom icons. File structure The file format consists of an 8 byte header, followed by any number of icons. Header Offset Size Purpose 0 4 Magic literal, must be "icns" (0x69, 0x63, 0x6e, 0x73) 4 4 Length of file, in bytes, msb first Icon data Offset Size Purpose 0 4 Icon type, see OSType below. 4 4 Length of data, in bytes (including type and length), msb first 8 Variable Icon data Icon types OSType Length (bytes) Size (pixels) Supported OS Version Description ICON 128 32×32 1.0 1-bit mono icon ICN# 256 32×32 6.0 1-bit mono