I'm having trouble serving a layer using the Cartodb JS API. Essentially, the script is being refused because of MIME type. I notice ?callback=vizjson has been appended to the end of the URL (see error below) but I haven't specified this to apply anywhere in the script (see immediately below).

cartodb.createLayer(map, 'http://samcomber.cartodb.com/u/samcomber/api/v2/viz/05ea0c96-0890-11e7-b110-0e98b61680bf/viz.json')

This is the error that is returned from Chrome debugger: Refused to execute script from 'http://samcomber.cartodb.com/u/samcomber/api/v2/viz/05ea0c96-0890-11e7-b110-0e98b61680bf/viz.json?callback=vizjson' because its MIME type ('application/json') is not executable, and strict MIME type checking is enabled.

This is the code for my project:

<!DOCTYPE html>
<title>Assignment Two</title>

<meta name="viewport" content="initial-scale=1.0, user-scalable=no" />

<meta http-equiv="content-type" content="text/html; charset=UTF-8"/>

<link rel="stylesheet" href="http://libs.cartocdn.com/cartodb.js/v3/themes/css/cartodb.css" />
html, body, #map {
  height: 100%;
  padding: 0;
  margin: 0;
<div id="map"></div>

<!-- include google maps lib -->
<script src="https://maps.googleapis.com/maps/api/js?sensor=false"></script>
<!-- include cartodb.js library -->
<script src="https://cartodb-libs.global.ssl.fastly.net/cartodb.js/v3/3.15/cartodb.js"></script>
  <!--Load the AJAX API-->

function main() {

    var map = L.map('map', { 
      center: [53.40, -2.89],
      zoom: 12,
      zoomControl: true

    L.tileLayer('https://maps.nlp.nokia.com/maptiler/v2/maptile/newest/normal.day.grey/{z}/{x}/{y}/256/png8?lg=eng&token=61YWYROufLu_f8ylE0vn0Q&app_id=qIWDkliFCtLntLma2e6O', {
      attribution: 'Nokia'

    var currentHover,
        newFeature = null

    cartodb.createLayer(map, 'http://samcomber.cartodb.com/u/samcomber/api/v2/viz/05ea0c96-0890-11e7-b110-0e98b61680bf/viz.json')
      .on('done', function(layer) {

      }).on('error', function() {
        console.log("some error occurred");

  window.onload = main;


What should I do?

  • Seeing the same thing when using createLayer with Google Maps, but only on certain layers. Have hundreds of layers to test. – knownasilya Mar 15 '17 at 14:15

I submitted https://github.com/CartoDB/cartodb.js/issues/1597 with this link. Carto acknowledges it's a bug and is working on resolving it.

| improve this answer | |
  • Thanks @knownasilya . Interestingly, this seems like an issue on Chrome only. – Sam Comber Mar 15 '17 at 14:19
  • Yeah, extra security. Should have been fixed yesterday. – knownasilya Mar 16 '17 at 19:17

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