Iframe Height Width. By default, iframes have a fixed height. The width attribute specifies the width of an <iframe>, in pixels.
That's fine if your content also has a fixed height but if your content's height changes you could easily end up looking at a double-scrollbar monstrosity like this Specifies the width and height of the iframe. Responsive iframes with CSS only — clean & cross-browser compliant code. By default, iframes have a fixed height.
Most of the styling attributes associated with <iframe> (and most other elements as well) have been deprecated.
Setting Iframe Height to Match Content Height.
On this page we present JavaScript that sets the height of an iframe to match the height of its content so that regular window scrollbars are used. By default, iframes have a fixed height. I've found someting like : myIFrame.contentWindow.document.body.scrollHeight.