(registered 2015-01-23 per RFC7519)   

Type Name: application
Subtype Name: jwt
Required Parameters: n/a
Optional Parameters: n/a
Encoding considerations: 8bit; JWT values are encoded as a series
      of base64url encoded values (some of which may be the empty
      string) separated by period ('.') characters.
Security Considerations: See the Security Considerations section
      of RFC7519
Interoperability Considerations: n/a
Published Specification: RFC7519
Applications that use this media type: OpenID Connect, Mozilla
      Persona, Salesforce, Google, Android, Windows Azure, Amazon Web
      Services, and numerous others
Fragment identifier considerations: n/a
Additional Information: Magic number(s): n/a, File extension(s):
      n/a, Macintosh file type code(s): n/a
Person & email address to contact for further information: Michael
      B. Jones, mbj&microsoft.com
Intended Usage: COMMON
Restrictions on Usage: none
Author: Michael B. Jones, mbj&microsoft.com
Change Controller: IESG
Provisional registration?  No