What is an ICNS file?
An ICNS file is a file format used on macOS to store icons for applications, folders, and other items. It is a container file format that can hold multiple image sizes and resolutions of the same icon.
ICNS files typically contain images in several resolutions, ranging from 16x16 pixels to 1024x1024 pixels, to accommodate different display sizes and resolutions on macOS devices. The file format uses a compression algorithm to reduce the file size of the images.
ICNS files can be created using various software tools, such as Icon Composer or Sketch, and can be assigned to various items on a macOS system, such as applications, folders, and documents. When an item is selected on a macOS system, the operating system retrieves the appropriate size and resolution of the icon from the ICNS file and displays it on the screen.
ICNS File Format - More Information
ICNS files are container files that can hold multiple image sizes and resolutions of the same icon using a technique called “icon family”. An icon family consists of a group of image resources, each representing the same icon but at different sizes or resolutions. Each image resource within an icon family has a unique type and ID, which identifies the image size and resolution. The different image sizes and resolutions are stored within the same ICNS file using different types and IDs.
When an item is selected on a macOS system, the operating system retrieves the appropriate size and resolution of the icon from the ICNS file using its type and ID, and displays it on the screen. This allows the macOS system to display high-quality icons on screens with different resolutions, such as on Retina displays, while maintaining a smaller file size.
ICNS files on macOS are similar to .ICO files on Windows in that they both serve as file formats for storing icons. Just like ICNS files, ICO files can contain multiple image sizes and resolutions of the same icon, which are used to display the icon on different screen sizes and resolutions on Windows devices.
However, there are some differences between ICNS and ICO files. For example, ICNS files can store higher resolution images than ICO files, which makes them better suited for use on high-resolution displays, such as Retina displays on macOS devices. Additionally, ICNS files can contain images with an alpha channel, allowing for transparent backgrounds, which is not supported in ICO files.
