The simplest way is to grab the size of the iframe’s contents when it loads, although that won’t dynamically handle changes in the size of the iframe’s contents. < iframe src = "https://example.com" onload = "this.style.height=(this.contentWindow.document.body.scrollHeight)+'px';" width = "100%" > </ iframe > To send a message from the embedded iframe to the parent document, use this code in the iframe’s document: