Failed to execute 'postMessage' on 'DOMWindow': The target origin provided does not match the recipient window's origin ('null')

Make sure the target window that you (or Facebook) is posting a message to, has completed loading. Most of the times I've gotten this error were when an iframe I was sending messages to had failed to load.

Another reason this could be happening is if you are using an iframe that has the sandbox attribute and allow-same-origin isn't set e.g.:

// page.html<iframe id="f" src="http://localhost:8000/iframe.html" sandbox="allow-scripts"></iframe><script type="text/javascript">    var f = document.getElementById("f").contentWindow;    // will throw exception    f.postMessage("hello world!", 'http://localhost:8000');</script>// iframe.html<script type="text/javascript">    window.addEventListener("message", function(event) {        console.log(event);    }, false);</script>

I haven't found a solution other than:

• add allow-same-origin to the sandbox (didn't want to do that)
• use f.postMessage("hello world!", '*');

To check whether the frame have been loaded, use onload function. Or put your main function in load: I recommend to use load when creating the iframe by js

 $('<iframe />', {   src: url,   id:  'receiver',   frameborder: 1,   load:function(){     //put your code here, so that those code can be make sure to be run after the frame loaded   }   }).appendTo('body');