Re: Difference in 1.4.10 Testing Approach

With the 320px approach, your viewport height is not equivalent to 256px. You’re basically simulating an unrealistically long mobile device. In order to be equivalent to the 1280px / 400% test, you would also have to shrink the responsive preview height (from 721px to 256 in your screenshot). Then you would get the same results for both tests.


Regards,

Hans Hillen

> On 20 Mar 2026, at 07:15, Tumelaire, Justin <Justin.Tumelaire@cengage.com> wrote:
> 
> Thank you, Patrick. I’m not sure if attachments come through but I will attempt them. Here is the description:
> In an eReader experience, when set at 1280px and zooming to 400% the reading pane containing the book content is almost entirely obscured by the navigation and menu options that are reflowed to the bottom of the screen because these components scale up with the zoom.
> When setting the viewport to 320px without zooming, the reading pane containing the book remains entirely visible. The navigation and menu options resize proportionally to the viewport. 
>  
> I appreciate it!
>  
> Justin
>  
>  
>  
> From: Patrick H. Lauke <redux@splintered.co.uk <mailto:redux@splintered.co.uk>>
> Sent: Thursday, March 19, 2026 1:57 PM
> To: w3c-wai-ig@w3.org <mailto:w3c-wai-ig@w3.org>
> Subject: Re: Difference in 1.4.10 Testing Approach
>  
> Functionally, both approaches are supposed to lead to the same end result (viewport width of 320 CSS px). What differences are you seeing? On 19/03/2026 17: 38, Tumelaire, Justin wrote: > I hope all is well. I’m finding that different groups
> Functionally, both approaches are supposed to lead to the same end 
> result (viewport width of 320 CSS px). What differences are you seeing?
>  
> On 19/03/2026 17:38, Tumelaire, Justin wrote:
> > I hope all is well. I’m finding that different groups test 1.4.10 Reflow 
> > using different methods:
> > 
> >  1. Set width to 1280 px (for vertically scrolling content), zoom to
> >     400% and test
> >  2. Change the viewport to 320px without adjusting zoom and test
> > 
> > In my experience, the results are different. What may create issues with 
> > a loss of content using option 1 are not issues when testing using 
> > option 2. Are both options acceptable for testing reflow? Does option 1 
> > catch a larger subset of potential issues?
> > 
> > Thank you!
> > 
> > Justin
> > 
>  
> -- 
> Patrick H. Lauke
>  
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>  
>  
> <320px.png><1280px_400zoom.png>