DICOMweb cannot be used directly inside Web browsers, as the browsers do not know how to handle the “application/dicom+xml” MIME type that is prescribed by the standard.
You will have to use either a command-line tool (such as “curl”), a HTTP toolkit (such as Python), or a JavaScript/AJAX script (e.g. through jquery) to query DICOMweb.
The browser handles JSON responses just fine, I can’t think of any reason for a browser to request the XML encoding (unless the server doesn’t support JSON encoding)
It shows how to make an XHR to a DICOMWeb server from JavaScript and parse the result. I know this worked against DCM4CHEE but don’t recall if I tested it against Orthanc.
Yes, the Orthanc server does support JSON encoding.
However, as the Web browser does not indicate that it accepts “application/json” in the HTTP headers of the request, Orthanc defaults to “application/dicom+xml”. This is the behavior I observe with Chromium and Firefox.