Will browsers choke if the response header of a JSONP payload has content type of "application/jsonp"?

Question

I am implementing a JavaScript app that will consume a set of services that are provided by a 3rd party. I am also the first person (guinea pig?) to be a consumer of this 3rd party's services. Their services will allow me to request JSON and JSONP. Now in the past, I've run into issues with browser compatibility where if the "Content-type" response header is set to:

application/json

and you are requesting JSONP, that some browsers will choke. To fix this, I've set JSONP response headers to:

application/javascript

I know this works and it's great, however this 3rd party team is saying that JSONP should have this response header:

application/jsonp

Now, application/jsonp is NOT a registered mime type, so I'm curious if there is any documentation or proof that I can send back to them asking to change the mime type to application/javascript for JSONP responses.

Put another way, will browsers choke with application/jsonp as the content-type, and if so, where can I direct this 3rd party services team?

I could test every browser, yes, but I also want to future-proof my app in case future browsers get pickier about mime types.

Thanks

Answer 1

Since this is not a valid mime-type, https://www.iana.org/assignments/media-types/media-types.xhtml I believe the best course of action is to always go with a known, supported method which in this case is setting the content-type to application/javascript for JSONP. There is no way to guarantee that browsers will support unregistered mime-types in the future.