Need fullscreen API

How to control fullscreen by player API?

When I make fullscreen with [iframe], it goes to fullscreen.

const dv= document.getElementById('cloudflare');

BUT after it, when try to cancel fullscreen with button of player, It’s not working.
I guess fullscreen-button works with [video] tag which I can not access as it’s inside of iframe.
So please make a API for fullscreen or fullscreen-button work with [iframe].

I second this request. My client is asking that their content displays in fullscreen when a User plays a video (which is being served though an iframe).

I abandon this request.
and start to use THIRD PARTY PLAYER such as shaka, videos.js, etc.
I use shaka and much satisfied than Cloudflare’s player. You can control much more.