 <p>You cantry it this way, it should work:</p> <pre><code>$.ajax({ type: "GET", url: "/grafana/dashboard", contentType: "application/json", beforeSend: function(xhr, settings){ xhr.setRequestHeader("some_custom_header", "foo");}, success: function(data){ $("#output_iframe_id").attr('src',"data:text/html;charset=utf-8," + escape(data)) } }); </code></pre>