MIME Type Detection in Internet Explorer

MIME Type Detection in Internet Explorer: "Uploaded MIME Types

When uploading files from the client to the Web server, Windows Internet Explorer uses FindMimeFromData to determine a MIME type. Where possible, FindMimeFromData returns hard-coded values from the list of Known MIME Types rather than relying on the MIME type value associated with the file extension in the system registry. In some cases, the detected MIME type can differ from the generally accepted value for backwards compatibility, as shown in the following table:
Standard MIME Type FindMimeFromData Returns
image/jpeg image/pjpeg
image/png image/x-png
Known MIME Types

FindMimeFromData tests for the following MIME types:
MIME Type Description
text/plain Plain text. Default if data is primarily text and no other type detected.
text/html HTML. Default if common tags detected and server does not supply image/* type.
text/xml XML data. Default if data specifies <?xml with an unrecognized DTD.
text/richtext Rich Text Format (RTF).
text/scriptlet Microsoft Windows script component.
audio/x-aiff Audio Interchange File, Macintosh.
audio/basic Audio file, UNIX.
audio/mid Internet Explorer 7 and later. MIDI sequence.
audio/wav Pulse Code Modulation (PCM) Wave audio, Windows.
image/gif Graphics Interchange Format (GIF).
image/jpeg JPEG image.
image/pjpeg Default type for JPEG images.
image/png Internet Explorer 7 and later. Portable Network Graphics (PNG).
image/x-png Internet Explorer 7 and later. Default type for PNG images.
image/tiff Tagged Image File Format (TIFF) image.
image/bmp Bitmap (BMP) image.
image/x-xbitmap Removed from Internet Explorer 8.
image/x-jg AOL Johnson-Grace compressed file.
image/x-emf Enhanced Metafile (EMF).
image/x-wmf Windows Metafile Format (WMF).
video/avi Audio-Video Interleaved (AVI) file.
video/mpeg MPEG stream file.
application/octet-stream Binary file. Default if data is primarily binary.
application/postscript PostScript (.ai, .eps, or .ps) file.
application/base64 Base64-encoded bytes.
application/macbinhex40 BinHex for Macintosh.
application/pdf Portable Document Format (PDF).
application/xml XML data. Must be server-supplied. See also 'text/xml' type.
application/atom+xml Internet Explorer 7 and later. Atom Syndication Format feed.
application/rss+xml Internet Explorer 7 and later. Really Simple Syndication (RSS) feed.
application/x-compressed UNIX tar file, Gzipped.
application/x-zip-compressed Compressed archive file.
application/x-gzip-compressed Gzip compressed archive file.
application/java Java applet.
application/x-msdownload Executable (.exe or .dll) file."