CSS Examples

The allowfullscreen attribute is used to enable fullscreen mode for an HTML element, such as a <iframe> or <video> element. The attribute can be added to the HTML element like so:

<iframe src="example.com" allowfullscreen></iframe>

You can also set the attribute using JavaScript:

document.getElementById("myiframe").allowFullscreen = true;

CSS can also be used to control the appearance of the element while in fullscreen mode. For example, to hide the element's controls while in fullscreen mode:

iframe::-webkit-full-screen {
  /* styles here */
}

Additionally, you can use :fullscreen pseudoclass to target the element when it is in fullscreen mode:

iframe:fullscreen {
  /* styles here */
}

You can also listen to the fullscreenchange event on the document to detect when the element enters and exits fullscreen mode.

document.addEventListener("fullscreenchange", function(event) {
  if (document.fullscreenElement) {
    console.log("Element entered fullscreen mode.");
  } else {
    console.log("Element exited fullscreen mode.");
  }
});

It's important to note that not all browsers support the fullscreen API and the allowfullscreen attribute, so you may want to provide a fallback or alternative for users on older browsers.