In my Ruby on Rails application I tried to upload an image through the POSTMAN REST client in Base64 format. When I POST the image I am getting a 406 Not Acceptable Resp
406 Not Acceptable The resource identified by the request is only capable of generating response entities which have content characteristics not acceptable according to the accept headers sent in the request.
406 happens when the server cannot respond with the accept-header specified in the request. In your case it seems application/json for the response may not be acceptable to the server.