Reversing macOS 26's .icon
With the release of MacOS 26 (Tahoe), we now have an additional application bundled with Xcode 26; Icon Composer. Icon Composer lets developers create "layered icons out of Liquid Glass from a single design" in
a new multi-layer format. This introduces the .icon extension, the standard format from Icon Composer. These files can then be imported into Xcode 26, and specified in the App Icons and Launch Screen settings for your project.
With this new proprietary format, we'll need to understand how the icons are stored and bundled to implement support for .icon files in our applications.
The .icon file itself is simply a folder, in which there is an icon.json file and an assets subfolder. This JSON file is what Icon Composer interprets. It's made up of key-valuepairs pointing to files within assets within a layers object along with other icon details like translucency, an sRGB for the gradient, shadow, etc.
See a sample icon.json for a simple icon made with Icon Composer:
{
"fill" : {
"automatic-gradient" : "extended-srgb:0.00000,0.47843,1.00000,1.00000"
},
"groups" : [
{
"layers" : [
{
"image-name" : "mobile-solid.svg",
"name" : "mobile-solid"
}
],
"shadow" : {
"kind" : "neutral",
"opacity" : 0.5
},
"translucency" : {
"enabled" : true,
"value" : 0.5
}
}
],
"supported-platforms" : {
"circles" : [
"watchOS"
],
"squares" : "shared"
}
}
As a takeaway, the .icon format seems simple to reproduce. In regards to implementation, we still see .png files within the .app, however the assets.car is signifigantly modified when working with .icon rather than the current .xcassets.