Operating systems use "container" formats (like .ico for Windows or .icns for macOS) that house multiple versions of the same icon to ensure it looks sharp at any scale. Icons (Design basics) - Win32 apps | Microsoft Learn
Windows offers three methods: the scroll wheel, the right-click menu, or keyboard shortcuts. icon size desktop
Most operating systems provide quick ways to toggle between these sizes: Operating systems use "container" formats (like
Essential Guide to Desktop Icon Sizes: Optimization and Customization the right-click menu