The "typ" (type) Header Parameter is used by JWS applications to declare the
media type ([IANA.MediaTypes][]) of this complete JWS. This is intended for use
by the application when more than one kind of object could be present in an
application data structure that can contain a JWS; the application can use this
value to disambiguate among the different kinds of objects that might be
present. It will typically not be used by applications when the kind of object
is already known. This parameter is ignored by JWS implementations; any
processing of this parameter is performed by the JWS application. Use of this
Header Parameter is OPTIONAL.

Per [RFC 2045][RFC2045], all media type values, subtype values, and parameter names are
case insensitive. However, parameter values are case sensitive unless otherwise
specified for the specific parameter

To keep messages compact in common situations, it is RECOMMENDED that producers
omit an "application/" prefix of a media type value in a "typ" Header Parameter
when no other '/' appears in the media type value. A recipient using the media
type value MUST treat it as if "application/" were prepended to any "typ" value
not containing a '/'. For instance, a "typ" value of "example" SHOULD be used
to represent the "application/example" media type, whereas the media type
"application/example;part="1/2"" cannot be shortened to "example;part="1/2"".

The "typ" value "JOSE" can be used by applications to indicate that this object
is a JWS or JWE using the JWS Compact Serialization or the JWE Compact
Serialization. The "typ" value "JOSE+JSON" can be used by applications to
indicate that this object is a JWS or JWE using the JWS JSON Serialization or
the JWE JSON Serialization. Other type values can also be used by applications.

[IANA.MediaTypes]: https://www.iana.org/assignments/media-types/media-types.xhtml
[RFC2045]: https://tools.ietf.org/html/rfc2045