Foolproof way to detect if this page is INSIDE a cross-domain iframe

Question

An answer to \"Foolproof way to detect if iframe is cross domain\" describes a method to test if an iframe on a page points to a same-domain or cross-domain page, working ar

Answer 1

I attempted to use referer to determine cross-domain, but I discovered it was unreliable on many sites. Maybe someone will find this useful.

function IsCrossDomainFrame() {
    if( parent === window ) return false; //not a frame
    var parentLocation = new URL(document.referer);//the referer of an iframe is the parent
    return (parentLocation.protocol !== location.protocol ||
            parentLocation.hostname !== location.hostname ||
            parentLocation.port     !== location.port);
}

Protocol, hostname, and port determine cross-domain.