Summary
Meta properties and directives that prevent zooming or initiate delayed page refreshes impede access for users with low vision and who need additional time to consume the content.
Techniques
-
Do not disable zooming with the
viewport/user-scalabe=noproperty. -
Do not prevent zooming by setting the
viewport/maximum-scaleproperty to a value less than "2.0". -
Do not use the
meta-refreshpragma directive with a value greater than "0". [[WCAG-3.2.5]]
Example
The following viewport tag scales the page to the device size (initial-scale=1.0)
but allows the user to zoom the page up to 5x its initial size (maximum-scale=5.0).
<meta
name="viewport"
content="initial-scale=1.0;maximum-scale=5.0"/>The following meta tag will immediately redirect the user agent to new-page.html.
<meta
http-equiv="refresh"
content="0;url=new-page.html"/>Explanation
Disabling the ability to zoom a page prevents users from being able to enlarge the content to a size that is more comfortable for them to read at. Similarly, setting a maximum scale less than double the initial size limits minimums for readability required by WCAG.
It is not normal for publications to make use of page redirects in packaged formats like EPUB. For web-hosted publications, consider using a HTTP redirect to send users to a replacement page.
If it is necessary to refresh the content of a page, provide the user the option to initiate the refresh.