Access parent URL from iframe

I just discovered a workaround for this problem that is so simple, and yet I haven't found any discussions anywhere that mention it. It does require control of the parent frame.

In your iFrame, say you want this iframe: src="http://www.example.com/mypage.php"

Well, instead of HTML to specify the iframe, use a javascript to build the HTML for your iframe, get the parent url through javascript "at build time", and send it as a url GET parameter in the querystring of your src target, like so:

<script type="text/javascript">
  url = parent.document.URL;
  document.write('<iframe src="http://example.com/mydata/page.php?url=' + url + '"></iframe>');
</script>

Then, find yourself a javascript url parsing function that parses the url string to get the url variable you are after, in this case it's "url".

I found a great url string parser here: http://www.netlobo.com/url_query_string_javascript.html

If your iframe is from another domain, (cross domain), you will simply need to use this:

var currentUrl = document.referrer;

and - here you've got the main url!

Yes, accessing parent page's URL is not allowed if the iframe and the main page are not in the same (sub)domain. However, if you just need the URL of the main page (i.e. the browser URL), you can try this:

var url = (window.location != window.parent.location)
            ? document.referrer
            : document.location.href;

Note:

window.parent.location is allowed; it avoids the security error in the OP, which is caused by accessing the href property: window.parent.location.href causes "Blocked a frame with origin..."

document.referrer refers to "the URI of the page that linked to this page." This may not return the containing document if some other source is what determined the iframe location, for example:

• Container iframe @ Domain 1
• Sends child iframe to Domain 2
• But in the child iframe... Domain 2 redirects to Domain 3 (i.e. for authentication, maybe SAML), and then Domain 3 directs back to Domain 2 (i.e. via form submission(), a standard SAML technique)
• For the child iframe the document.referrer will be Domain 3, not the containing Domain 1

document.location refers to "a Location object, which contains information about the URL of the document"; presumably the current document, that is, the iframe currently open. When window.location === window.parent.location, then the iframe's href is the same as the containing parent's href.