References

Beginner-friendly references for web development, with live, editable examples.

The HTML allowfullscreen attribute

Attribute All modern browsers Updated
Quick answer

The HTML allowfullscreen attribute allows the framed content to enter fullscreen via the Fullscreen API. It is used on the <iframe> element.

Overview

The allowfullscreen attribute lets an iframe go fullscreen. It is used on the <iframe> element.

It configures embedded content: what is embedded, what capabilities it is granted, and how it is sandboxed. With third-party content, these attributes are your main security controls.

Syntax

<iframe src="player.html" allowfullscreen></iframe>

Values

Value
A boolean attribute: present or absent.

Best practices

  • Give every <iframe> a descriptive title.
  • Sandbox untrusted content with sandbox, and avoid combining allow-scripts with allow-same-origin for untrusted sources.
  • Grant only the features a frame needs with the allow attribute.
  • Defer off-screen frames with loading="lazy".

Frequently asked questions

What does the allowfullscreen attribute do?
Lets an iframe go fullscreen.
How do I make an iframe secure?
Restrict untrusted content with sandbox, grant minimal features with allow, and never pair allow-scripts with allow-same-origin for untrusted sources.
How do I embed inline HTML in an iframe?
Use the srcdoc attribute to supply the HTML directly instead of a src URL.
Which elements use the allowfullscreen attribute?
It is an element-specific attribute, used on the <iframe> element.
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