ContentType is a String property that indicates the media type used to represent an entity body, and contains a registered Internet Assigned Number Authority (IANA) media type. HTTP uses ContentType to provide open and extensible data typing and type negotiation. 

ContentType contains type, subtype, and parameter attribute name components significant to the processing of a media-type. 

Any HTTP/1.1 message containing an entity body should include a ContentType value defining the media type of that body. The default value for media type should be "application/octet-stream".