RE: Parallax and vestibular disorders



This is a really interesting question.


I have always covered automatic background scrolling (like on single page apps) under 2.2.2, but user-initiated, and animation of page content, are new parameters indeed, at least for 2.2.2. 


​​​​​I have added COGA to this discussion to see what they have discussed around this issue.


Thanks for bringing this up!




* katie *


Katie Haritos-Shea 
Principal ICT Accessibility Architect (WCAG/Section 508/ADA/AODA)


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From: Alastair Campbell [] 
Sent: Wednesday, July 27, 2016 10:51 AM
To: WCAG WG <>
Subject: Parallax and vestibular disorders


Hi everyone,


This might have been covered somewhere (COGA?), but I couldn’t find it if it has.


Has anyone considered new criteria for people with vestibular type issues?


It isn’t something I’m expert on, but there’s a good overview here: 


The issue that doesn’t seem to be covered is when you scroll a page (usually vertically, but sometimes horizontally) and things move at different speeds. E.g. the background moves more slowly than the foreground to give an impression of depth/distance.


That can trigger disorientation, nausea and/or loss of balance. When iOS 7 came out quite a lot of people reported motion sickness [1].


It is in the same area as 2.2.2 (Pause, Stop, Hide) but that doesn’t cover a scrolling based mechanism. (It does mention scrolling, but I read that as something that scrolls on its own, not that the animation happens whilst the user scrolls the page.)


You might argue the user is in control, but if they have to scroll to use it, they cannot use it (see the examples in the alistapart article above).

As an example (if you don’t have any disorder) try scrolling this page: 


You don’t have to use that mechanism, but if you do, whoosh! I’ve brought that example up for magnification users before, but it must be terrible for people with vestibular issues.


Off the top of my head an SC could be something like:

2.x.x User initiated animation:  For animation triggered by a user action (such as scrolling) there is a mechanism for the user to pause, stop or hide the animation whilst still performing the same action. (Level AA?)


I think it needs narrowing down, but I wanted to see if it is worth proposing or if someone already had?


Kind regards,




1] A poll at not scientific by any means but that’s quite a lot of people reporting an issue.




Alastair Campbell <> 

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Received on Wednesday, 27 July 2016 15:54:55 UTC