The Accept Header Field is used to specify Media Types acceptable to the user agent. It has the following syntax:

Accept = 1#(media-range [weight])

The Accept Header Field value shall be a comma-separated list of one or more media ranges acceptable in the response. See [RFC7231] Section 5.3.2.

A media range is either a media-type or a wildcard. Wildcards use the asterisk ("*") to group Media Types into ranges, with <type>/* indicating all subtypes of that type, and */* indicating all Media Types. For example, the media range image/* matches image/jpeg, which is the default Media Type for the Single Frame Image Resource Category, and text/* matches text/html, which is the default Media Type for the Text Resource Category. DICOM specifies that the */* media range matches the default Media Type for the target's Resource Category. If no default Media Type is defined for a Resource Category, then any Media Type from the Resource Category is acceptable.

If the response might contain a payload, an Accept Header Field shall be present in the request.

If the origin server receives a request without an Accept Header Field, but that might have a response payload, it shall return a 406 (Not Acceptable).

Any Accept Header Field values, including Media Type parameters, that are not valid or not supported shall be ignored by the origin server.