SIA-R47<meta name="viewport"> elements do not prevent zoom

Accessibility requirements

This rule tests conformance of the following accessibility requirements:

Description

This rule checks that the <meta> element retains the user agent ability to zoom.

Applicability

This rule applies to every <meta> element with a name attribute whose value is a case-insensitive match for viewport and has a content attribute which defines either the user-scalable or maximum-scale property.

Note: The content attribute is mapped into a list of property/value pairs in a user-agent specific manner.

Expectations

  1. For each test target, the content attribute does not:

    • specify the property user-scalable with a value of fixed; nor
    • specify the property maximum-scale with a value of less than 2.

Assumptions

Accessibility support

Desktop browsers ignore the viewport <meta> element, and most modern mobile browsers either ignore it by default or have an accessibility option which will allow zooming. This rule is not relevant for desktop browsers, nor for most modern mobile browsers. Only users with older mobile browsers can experience issues tested by this rule.

Implementation details

Alfa maps the content attribute according to this parsing algorithm.

Examples

Acknowledgments

This document includes material copied from or derived from https://www.w3.org/WAI/standards-guidelines/act/rules/b4f0c3/. Copyright © 2025 W3C® (MIT, ERCIM, Keio, Beihang).