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WCAG 1.4.4 Resizing Text and Zoom


From: Alan Zaitchik
Date: Nov 15, 2021 6:51PM

This is really long. I apologize, but I wanted to expose the reasoning behind my question.

My question concerns WCAG 1.4.4 (“Resize Text”), viz. whether it is enough to test with browser zoom or must one test with setting font size to 200% the system default or medium font size. This problem is acute for one of our applications where we (alas) inherited dependence on a third-party software package that builds grids into which we stream data; these grids do not adequately resize to accommodate resized text, although they work just fine with browser zoom.
Reading through the WCAG materials I find a certain ambiguity regarding the satisfaction conditions for 1.4.4. On the one hand “Understanding Success Criterion 1.4.4: Resize text” (https://www.w3.org/WAI/WCAG21/Understanding/resize-text.html) says:
The scaling of content is primarily a user agent responsibility. User agents that satisfy UAAG 1.0 Checkpoint 4.1 allow users to configure text scale. The author's responsibility is to create Web content that does not prevent the user agent from scaling the content effectively.
That seems to say that where the user agent has a mechanism to scale content the author’s responsibility is simply not to prevent the user agent mechanism from working. Zoom scales content, and our code does not prevent that. So arguably we’re ok.

But read on…

… The author cannot rely on the user agent to satisfy this Success Criterion for HTML content if users do not have access to a user agent with zoom support. For example, if they work in an environment that requires them to use IE 6.

If the author is using a technology whose user agents do not provide zoom support, the author is responsible to provide this type of functionality directly or to provide content that works with the type of functionality provided by the user agent.

Can we rely on the user agent zoom where the browser does have zoom? We support only recent browsers, all of which support zoom. IE 6 is definitely not our concern. Again, it could be argued that we are ok relying on zoom. But surely some users might not use zoom or even know of its possibility! So perhaps we cannot rely on it.

Now for a statement that seems very clear.

Technique G142 “Using a technology that has commonly-available user agents that support zoom” for SC 1.4.4 (https://www.w3.org/WAI/WCAG21/Techniques/general/G142.html) explicitly states:
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.

The examples given are IE 7 and Adobe Reader zoom or magnification tools. What could be more explicit than that?

And yet … Many (most?) people with vision disabilities do set their font size larger at the system level and do not use browser zoom, even when it is available. So even if browser-delivered content could be zoomed is it appropriate to require users to do so where rescaling font size fails to keep all content available? It could certainly be argued that the spirit of 1.4.4 is not respected for users chancing upon pages where their normally rescaled text suddenly is illegible, and an additional action is required of them. On mobile devices some users will have great difficulty with pinching to zoom.

What is your practice regarding this Satisfaction Condition? In your experience is zoom or text resizing the dominant method by which users with impaired vision enlarge text?