Chrome refuses to execute an AJAX script due to wrong MIME type

146
votes

I'm trying to access a script as JSON via AJAX, which works fine on Safari and other browsers but unfortunately will not execute in Chrome. It's coming with the following error:

Refused to execute script from '*' because its MIME type ('application/json') is not executable, and strict MIME type checking is enabled.

Here's the request:

$.ajax({
    url: "http://some_url/test.json?callback=?",
    type: "GET",
    dataType: 'json',
    cache: true,
    success: function (data, status, error) {
      console.log('success', data);
    },
    error: function (data, status, error) {
      console.log('error', data, status, error);
    }
});

Does anyone have a workaround for this?

7
javascriptjqueryajaxjsongoogle-chrome
So, what is this ressource? A JSONP script, or a JSON file? Does its MIME type match that? Apparently not. No need for a workaround, just fix it. – Bergi
removing the callback and using dataType jsonp does not fix the issue – Paul Nelligan
I meant, fix the server response. – Bergi
@Bergi: what if the server is outside of the OP's control? Maybe he's trying to use an external API such as LinkedIn. – Dan Dascalescu
@DanDascalescu: He should report this as a bug, because it makes the API unusable. While waiting for this to be fixed, he can use a proxy that changes mime type or content. – Bergi

7 Answers

72
votes

By adding a callback argument, you are telling jQuery that you want to make a request for JSONP using a script element instead of a request for JSON using XMLHttpRequest.

JSONP is not JSON. It is a JavaScript program.

Change your server so it outputs the right MIME type for JSONP which is application/javascript.

(While you are at it, stop telling jQuery that you are expecting JSON as that is contradictory: dataType: 'jsonp').

57
votes

If your proxy server or container adds the following header when serving the .js file, it will force some browsers such as Chrome to perform strict checking of MIME types:

X-Content-Type-Options: nosniff

Remove this header to prevent Chrome performing the MIME check.

11
votes

FYI, I've got the same error from Chrome console. I thought my AJAX function causing it, but I uncommented my minified script from /javascripts/ajax-vanilla.min.js to /javascripts/ajax-vanilla.js. But in reality the source file was at /javascripts/src/ajax-vanilla.js. So in Chrome you getting bad MIME type error even if the file cannot be found. In this case, the error message is described as text/plain bad MIME type.

2
votes

For the record and Google search users, If you are a .NET Core developer, you should set the content-types manually, because their default value is null or empty:

var provider = new FileExtensionContentTypeProvider();
app.UseStaticFiles(new StaticFileOptions
{
    ContentTypeProvider = provider
});
1
votes

I encountered this error using IIS 7.0 with a custom 404 error page, although I suspect this will happen with any 404 page. The server returned an html 404 response with a text/html mime type which could not (rightly) be executed.

0
votes

In my case, I use

$.getJSON(url, function(json) { ... });

to make the request (to Flickr's API), and I got the same MIME error. Like the answer above suggested, adding the following code:

$.ajaxSetup({ dataType: "jsonp" });

Fixed the issue and I no longer see the MIME type error in Chrome's console.

0
votes

if application is hosted on IIS, make sure Static Content is installed. Control Panel > Programs > Turn Windows features on or off > Internet Information Services > World Wide Web Services > Common HTTP Features > Static Content.

I faced this problem when trying to run an existing application on a new IIS 10.0 installation