People With Vestibular Disorders and Motion Sensitivity
Parallax, autoplay video, and large scroll-triggered animation can make someone physically ill. The fix is one media query.
For some users, your scroll animation is a symptom trigger, not a delight.
The reaction is physical and can outlast the visit: dizziness, nausea, disorientation, or a migraine that costs the rest of the day. Large background movement, parallax layers moving at different speeds, and full-width autoplay video are the most common triggers. The user does not file a bug report; they close the tab.
Scale: NIH-funded research has estimated that roughly 35% of U.S. adults aged 40 and over have experienced some form of vestibular dysfunction. (Source: NIDCD / NIH. Survey-based disability figures undercount — treat this as a floor.)
What they're using
- The operating system's Reduce Motion setting, exposed to CSS as prefers-reduced-motion
- Extensions that block animation and autoplay
- Avoidance — users leave and do not come back
4 barriers we find most often, and the criteria behind them.
Motion triggered by scrolling
Parallax and scroll-driven animation are the most frequently cited triggers. The criterion that covers this directly — 2.3.3 Animation from Interactions — is Level AAA, so a site can be fully Level AA conformant and still make people ill.
Not required at AA: WCAG 2.3.3 Animation from Interactions is Level AAA. Not required for AA conformance; we recommend it anyway.
Content that moves or auto-advances
Carousels, tickers, and animated backgrounds that run for more than five seconds need a mechanism to pause, stop, or hide them.
Success criteria: 2.2.2 Pause, Stop, Hide A
Autoplaying video and audio
Motion plus sound the user did not ask for, often before the page has finished loading.
Success criteria: 1.4.2 Audio Control A · 2.2.2 Pause, Stop, Hide A
Ignoring the user's stated preference
If someone has turned on Reduce Motion at the OS level, they have already told you. Not honoring prefers-reduced-motion means overriding an explicit accommodation — and honoring it is a handful of CSS lines.
Not required at AA: No Level AA criterion requires this. It is the clearest example on this page of conformance and accessibility not being the same thing.
The changes that actually remove the barrier.
Honor prefers-reduced-motion
Wrap non-essential animation in the media query and reduce it to a cross-fade or nothing. This is a handful of CSS lines and it resolves most of the risk.
Give carousels and tickers a real pause control
Visible, keyboard-reachable, and it should actually stop the motion rather than just the timer.
Do not autoplay
If video must autoplay, mute it, keep it short, and provide a control that stops it.
Keep large motion off the critical path
Animation on a marketing hero is a choice; animation between a user and a permit application is a barrier.
Three tests you can run before you call anyone.
- Turn on Reduce Motion in your OS settings and reload every animated page. If anything still moves, that is the finding.
- Load the homepage and count how many things move without you asking.
- Check that every carousel has a pause control you can reach with Tab.
If any of those go badly, you have your answer and you did not need a vendor to get it. What a vendor is for is the part after: knowing which of the 55 criteria that maps to, how deep it goes, and what it costs to fix properly rather than patch.
Run the Free CheckerWhere this shows up in practice
Other people the standard was written for.
People With Photosensitive Epilepsy
The smallest affected group and the highest-severity consequence on this entire list. There is no partial credit here.
Read the profileOlder Adults
Aging rarely produces one disability. It produces slightly reduced vision, hearing, dexterity, and processing speed simultaneously — which compounds.
Read the profileAll 55 Success Criteria
Every Level A and AA criterion in plain language, with the failure we see most often for each.
Reference