Using the srcdoc Attribute

The srcdoc attribute can be used (instead of the src attribute) to specify the exact contents of the iframe as a whole HTML document. This will yield an IFrame with the text “IFrames are cool!”

<iframe srcdoc="<p>IFrames are cool!</p>"></iframe>

If the srcdoc attribute isn’t supported by the browser, the IFrame will instead fall back to using the src attribute, but if both the src and srcdoc attributes are present and supported by the browser, srcdoc takes precedence.

<iframe srcdoc="<p>Iframes are cool!</p>" src="base.html"></iframe>

In the above example, if the browser does not support the srcdoc attribute, it will instead display the contents of the base.html page.