// mime type · image type
image/x-icon
Icon (favicon) · .ico
What image/x-icon is
image/x-icon is the classic favicon format (.ico), which can bundle several sizes in one file. Modern sites often use PNG or SVG favicons instead.
How it's used
You'll see this as a Content-Type value on requests and responses — for example Content-Type: image/x-icon. It's the type associated with the .ico file extension. Image types tell the browser how to decode and render a picture.