HTML `allowfullscreen` Attribute

The allowfullscreen attribute is commonly used with <iframe> elements to allow embedded content to enter fullscreen mode. Without this attribute, users may not be able to expand videos or other embedded media to fill their entire screen.

Basic Example

<iframe
    src="https://www.youtube.com/embed/dQw4w9WgXcQ"
    width="560"
    height="315"
    allowfullscreen>
</iframe>

What happens?
When a user clicks the fullscreen button in the embedded video player, the browser allows the content to expand to fullscreen mode.

Why Use allowfullscreen?

Improves user experience for video content.
Allows presentations and interactive content to be viewed fullscreen.
Expected by users when viewing embedded media.
Supported by all modern browsers.

Common Use Cases

Content Type	Uses allowfullscreen?
YouTube Videos	Yes
Vimeo Videos	Yes
Interactive Maps	Sometimes
Embedded Presentations	Often

Modern Alternative

Some websites also use the allow attribute alongside allowfullscreen:

<iframe
    src="https://example.com"
    allow="fullscreen"
    allowfullscreen>
</iframe>

Including both attributes can help ensure compatibility with modern browser permission policies and embedded content requirements.

Browser Support