What is the correct JSON content type?

Question

I've been messing around with JSON for some time, just pushing it out as text and it hasn't hurt anybody (that I know of), but I'd like to start doing things properly.

I have seen so many purported "standards" for the JSON content type:

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

But which is correct, or best? I gather that there are security and browser support issues varying between them.

I know there's a similar question, What MIME type if JSON is being returned by a REST API?, but I'd like a slightly more targeted answer.

Answer 1

If you're calling ASP.NET Web Services from the client-side you have to use application/json for it to work. I believe this is the same for the jQuery and Ext frameworks.

Answer 2

JSON is a domain-specific language (DSL) and a data format independent of JavaScript, and as such has its own MIME type, application/json. Respect for MIME types is of course client driven, so text/plain may do for transfer of bytes, but then you would be pushing up interpretation to the vendor application domain unnecessarily - application/json. Would you transfer XML via text/plain?

But honestly, your choice of MIME type is advice to the client as to how to interpret the data- text/plain or text/HTML (when it's not HTML) is like type erasure- it's as uninformative as making all your objects of type Object in a typed language.

No browser runtime I know of will take a JSON document and automatically make it available to the runtime as a JavaScript accessible object without intervention, but if you are working with a crippled client, that's an entirely different matter. But that's not the whole story- RESTful JSON services often don't have JavaScript runtimes, but it doesn't stop them using JSON as a viable data interchange format. If clients are that crippled... then I would consider perhaps HTML injection via an Ajax templating service instead.

Application/JSON!

Answer 3

“application/json” is the correct JSON content type.

def ajaxFindSystems = {
  def result = Systems.list()
  render(contentType:'application/json') {
    results {
      result.each{sys->
        system(id:sys.id, name:sys.name)
      }
    }
    resultset (rows:result.size())
  }
}

Answer 4

The right MIME type is application/json

BUT

I experienced many situations where the browser type or the framework user needed:

text/html

application/javascript

Answer 5

PHP developers use this:

<?php
    header("Content-type: application/json");

    // Do something here...
?>

Answer 6

Extending the accepted responses, when you are using JSON in a REST context...

There is a strong argument about using application/x-resource+json and application/x-collection+json when you are representing REST resources and collections.

And if you decide to follow the jsonapi specification, you should use of application/vnd.api+json, as it is documented.

Altough there is not an universal standard, it is clear that the added semantic to the resources being transfered justify a more explicit Content-Type than just application/json.

Following this reasoning, other contexts could justify a more specific Content-Type.