For JSON data, there are different mime-types floating around the web:

  • application/json
  • text/javascript
  • text/json
  • text/x-json

At ruby-forum.com there is a nice discussion which points out, why it is best to use text/x-json. The already wide-spread application/json is not really correct as application is meant for data which can only be read after being processed. But as JSON is clear-text, you can read it somewhat without parsing. That's why the text branch is to be preferred. And as the json type is not yet approved, you have to use x-json - a nonstandard extension.