Manual:$wgTrustedMediaFormats

Details
List of trusted media-types and MIME types. MIME types are maintained by the IANA (Internet Assigned Numbers Authority). You may wish to consult a list of common MIME types and their associated file extensions before trying to determine what to add to $wgTrustedMediaFormats. Use the MEDIATYPE_xxx constants to represent media types.

Files that do not match an entry on this list will have the content of the system message  MediaWiki:Mediawarning  displayed on the image description page. The default message is: