When movement causes an action on a device, that is motion actuation. In terms of the Web Content Accessibility Guidelines, motion actuation is defined as the movement of the device or a movement by the user. So for example, changing a digital photo's orientation by tilting the phone is a device motion. Unlocking a computer by waving at a sensor is a user motion. Both are types of motion actuation.
Motion actuation can be a helpful accessibility feature. Users who use or prefer larger movements instead of precise touches or clicks can take advantage of these features.
However, motion actuation can also be a barrier. Some users cannot move the device easily or at all, such as if it is bolted to a desk or wheelchair. Users with motor disabilities may not be able to consistently match the required motion, or may accidentally activate motion functions if they experience tremors or other unintended movements.
The solution is to ensure that if you include motion actuation, that you also have methods to both:
- Perform the same function without motion actuation
- Disable the motion actuation
For example, a user typing a text message on an iPhone can shake their phone to delete the text message, a feature called “Shake to Undo.” Users can perform the same function using the keyboard's delete button, which doesn’t require a device movement. Users can also disable “Shake to Undo” using the phone’s accessibility settings.
As with many accessibility practices, flexibility and user control mean people can use configurations that work for them.
For a step-by-step guide in reviewing this and other web accessibility requirements, explore the Guided Manual WCAG Audit Tool from Accessible Web.