2.5.4 Motion Actuation WCAG 2.1 Level A

Functionality that can be operated by device motion or user motion can also be operated by user interface components and responding to the motion can be disabled to prevent accidental actuation, except when:

  • Supported Interface:

The motion is used to operate functionality through an accessibility supported interface;

  • Essential:

The motion is essential for the function and doing so would invalidate the activity.

Description

Have you observed popping an alert ‘undo typing’ when you are texting or chatting on your phone while travelling on a car or bus? This is probably because your phone in the hand is shaken. Your phone or the website or application have a feature ‘shake to undo’. Because of the trembling in hands while in travel the shake to undo is just invoked accidently.

In modern applications content authors can create experiences that are dependent on shake, tilt or gesturing towards the devices.

Similar to task dependent on shake, tilting the phone can take the user to next or previous screen, waving the hand before the camera to trigger an activity or any motion dependent actions are simply called as motion actuations.

Motion actuation is difficult for those who place their device on a fixed position such as on a hand rest of a wheel chair. It is also problematic for those who have motor related challenges. While some users cannot perform tasks related to motion actuation, some others may trigger these tasks involuntarily because of challenges such as trimmers or situations such as traveling.

While success criteria 2.5.4 motion actuation is problematic for many, these situations can also be handled easily by the content authors.

How to handle 2.5.4 motion actuation

The primary check content authors have to verify is to see the motion actuation of the website or application is respecting the user setting at the operating system level or not. For example, if the user turns-off the motion actuation related setting in the operating system, any activity that is dependent on motion actuation should not be triggered either intentionally or accidentally.

Alternately, all activities that are dependent on motion actuation must be available for the user as part of the user interface. For example, if shaking the device performs undo typing for the text entered in an input field, the same activity  can also be performed by tapping on the clear button adjacent to the input control.

Exemptions for 2.5.4 motion actuation

As discussed earlier in the article, if an accessibility supported interface such as an UI control to perform the same activity as the motion actuation does, this success criteria is exempted.

Another exemption is the essential exemption. For example, a pedometer that relies on device motion to count steps. The device sensor and the data collected with the motion of the device are essential for some applications. Such activity is exempted from this success criteria.

Who benefits with 2.5.4 motion actuation?

  • Users who cannot move their devices partly or completely because of their physical challenges or because the device is placed on a fixed position such as a hand rest on a wheel chair.
  • Users who involuntarily shakes the device because of challenges such as trimmers in hands or situations such as in travel.

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