A Content-Type of "image" indicates that the body contains an image. The subtype names the specific image format. These names are case insensitive. Two initial subtypes are "jpeg" for the JPEG format, JFIF encoding, and "gif" for GIF format [GIF].
The list of image subtypes given here is neither exclusive nor exhaustive, and is expected to grow as more types are registered with IANA, as described in Appendix E.
The formal grammar for the content-type header field for data of type image is given by:
image-type := "image" "/" ("gif" / "jpeg" / extension-token)