image/vnd.microsoft.icon

The officially registered media type for Windows icons and favicons — registered by a third party in 2003, long after the format itself shipped with Windows 3.0. In practice almost nobody sends it: the unregistered alias image/x-icon dominates real traffic, and browsers accept either. An ICO is a small directory of images at multiple sizes and depths, which is why a single favicon.ico can look right at 16, 32, and 48 pixels.

Defined by IANA registration — image/vnd.microsoft.icon · IANA registration. Registry facts from the IANA media-types registry via mime-db.