HTML allow Attribute: Reference and Examples

The allow attribute is a small instruction attached to an HTML element. Its job is to permissions-policy features permitted in an iframe. It is easier to remember when you can see it in a real piece of markup.

What allow is used for

Permissions-policy features permitted in an iframe. The attribute appears inside an element’s opening tag. Depending on its definition, it may take a specific string, a number, an enumerated keyword, or be a boolean attribute.

The example below uses it in a iframe context. Other elements may support it too, or may give the same attribute a different meaning.

Example you can try

<section>
    <iframe title="Embedded lesson" src="/lesson-preview" allow="fullscreen; autoplay"></iframe>
</section>

How the example works

Look for allow in the snippet. Here the example shows the value fullscreen; autoplay. This is a concrete input the browser can interpret; it is not just text shown to the reader.

The embedding page can grant only permissions consistent with the site’s and browser’s broader permissions policies.

Values and important behavior

Use the value format shown by the HTML definition. Do not assume that a value accepted in one attribute also works in another. When a browser ignores an invalid value, inspect the element and correct the markup.

This detail matters most when the page receives user input, navigates to another document, or loads an external resource. In those cases, check the browser behavior and any server-side requirements separately.

Small practice task

Copy the code and change allow to another sensible value, or remove it entirely if it is optional. Test the difference in the browser and inspect any submitted value or network request.

Common Beginner Mistakes

• The embedding page can grant only permissions consistent with the site’s and browser’s broader permissions policies.
• Using allow on an element that does not support it.
• Believing that an HTML hint or client-side check replaces real server validation or a security policy.

Key Takeaways

• allow is used to permissions-policy features permitted in an iframe.
• The embedding page can grant only permissions consistent with the site’s and browser’s broader permissions policies.
• Choose valid values and test the result instead of guessing what the browser will do.