What Is the Correct Mime-Type for JSON and JSONP?

In this article, we look at the correct mime types for JSON and JSONP as defined in the official IANA media types list.

Media Type	Mime-type	RFC
JSON	`application/json`	RFC 4627
JSONP	`application/javascript`	RFC 4392

JSON Mime Type

RFC 4627 specifies that the correct mime-type for JSON is:

application/json

If you wish to support IE7 (or below), using application/json might not work as expected because Internet Explorer will associate application/json to an application installed on the client-side and will show a "Save As" disalog box. In that case, the solution might be to use the mime-type text/javascript instead.
As a precaution, you should avoid serving json with the content-type text/html as it can be a potential security risk.

JSONP Mime Type

For JSONP the correct mime-type would be the same as it is for JavaScript (as stated in RFC 4392), which is:

application/javascript

It is so because the response body of a JSONP response is essentially JavaScript.

Variants in the Wild:

Be aware of variants in the wild, which are either obsolete or non-standard and are discouraged for use. Some notable examples are:

text/javascript
text/ecmascript
text/jscript
text/livescript
text/x-javascript
text/x-ecmascript
application/x-javascript
application/x-ecmascript
application/javascript
application/ecmascript

Serving media with an incorrect mime-type can potentially lead to unwanted behavior and/or security risks.

This post was published 09 Jan, 2020 (and was last revised 03 Jun, 2020) by Daniyal Hamid. Daniyal currently works as the Head of Engineering in Germany and has 20+ years of experience in software engineering, design and marketing. Please show your love and support by sharing this post.