RE: [EXTERNAL] RE: Difference in 1.4.10 Testing Approach

There definitely is a difference between testing "full screen" web applications on a 320px wide window vs a 1280px wide window with 400% zoom. Many full screen web applications are set to 100% width and 100% height, and do not have vertically scrolling content when magnified.

I have been looking at a lot of GIS applications, such as Esri Dashboards or Experience Builder web apps, which are full screen and used by most government agencies and many organizations. Almost all of these applications fail the magnification and reflow requirements, and the behavior of the map also changes when you view it with "real" page magnification.

From: Guy Hickling <guy.hickling@gmail.com>
Sent: Thursday, March 19, 2026 1:10 PM
To: WAI Interest Group discussion list <w3c-wai-ig@w3.org>
Subject: [EXTERNAL] RE: Difference in 1.4.10 Testing Approach

This illustrates what I have always argued, that 1.4.10 is about zooming to 400%, so that is how we should test it. Testing on a  window artificially reduced to the required pixel size is effectively just using an "emulator", it is not testing the real thing! If the developer does something really clever or unusual, perhaps using JavaScript, you run the risk of not finding issues (or oppositely finding too many) that the real life users using real life zoom actually see.