To make YouTube iframe embed full screen with HTML, we set the allowfullscreen attribute.
For instance, we write
<iframe
src="your_page_url"
allowfullscreen="allowfullscreen"
mozallowfullscreen="mozallowfullscreen"
msallowfullscreen="msallowfullscreen"
oallowfullscreen="oallowfullscreen"
webkitallowfullscreen="webkitallowfullscreen"
>
</iframe>
to set the allowfullscreen attribute to allowfullscreen to allow full screen.
We set the equivalent attributes for other browsers to allow full screen on them.
