Allow developers to selectively enable and disable use of Fullscreen through the Feature-Policy HTTP header or the <iframe> "allow" attribute. The identifier for the feature in policies is "fullscreen". By default, fullscreen is allowed in all top-level documents, and in same-origin frames. This is similar to the existing <iframe> "allowfullscreen" attribute, but allows control over which origins will be allowed to use the feature when hosted inside of the frame.
Samples: https://fullscreen.featurepolicy.rocks/ https://fullscreen.featurepolicy.rocks/allow.html