Techniques for WCAG 2.0

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G142: Using a technology that has commonly-available user agents that support zoom


All technologies with user-agent provided zoom capability.

This technique relates to:

User Agent and Assistive Technology Support Notes

The Zoom functionality in IE 7.0 does not always scale uniformly when absolute positioning is used and the page is scaled smaller. Microsoft Internet Explorer 7.0 supports both Zoom and Text Size changes for fonts set with %, em or named sizes.

Opera 9 supports Zoom.

Firefox 2 and below supports only text size changes, but can change the size of pt and px fonts as well as %, em and named sizes.

Firefox 3 supports both zoom and text size changes.


The objective of this technique is to ensure content can be scaled uniformly by using a Web technology supported by user agents that change text size via a Zoom tool.

Content authored in technologies that are supported by user agents that can scale content uniformly (that is, zoom into content) satisfy this Success Criterion. Because this technique relies completely on user agent functionality, it is critical to test with a wide variety of user agents.

This technique requires that the zoom function preserve all spatial relationships on the page and that all functionality continues to be available.


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  1. Display content in a user agent

  2. Zoom content to 200%

  3. Check whether all content and functionality is available

Expected Results

If this is a sufficient technique for a success criterion, failing this test procedure does not necessarily mean that the success criterion has not been satisfied in some other way, only that this technique has not been successfully implemented and can not be used to claim conformance.

Techniques are Informative

Techniques are informative—that means they are not required. The basis for determining conformance to WCAG 2.0 is the success criteria from the WCAG 2.0 standard—not the techniques. For important information about techniques, please see the Understanding Techniques for WCAG Success Criteria section of Understanding WCAG 2.0.