The standard Media Type (formerly known as MIME types) is application/pdf
. The assignment is defined in RFC 3778, The application/pdf Media Type, referenced from the Media Types registry.
Media Types are controlled by a standards body, The Internet Assigned Numbers Authority (IANA). This is the same organization that manages the root name servers and the IP address space.
The use of x-pdf
predates the standardization of the Media Type for PDF. Media Types in the x-
namespace are considered experimental, just as those in the vnd.
namespace are considered vendor-specific. x-pdf
might be used for compatibility with old software.