Success Criterion 2.5.4 Motion Actuation (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;
The motion is essential for the function and doing so would invalidate the activity.
We sometimes see that actions/functionalities in the digital space would take place as soon as there are certain movements either with the device or user. the functionalities/actions related to user motion or device motion are mostly seen in the mobile native apps and rarely seen in the mobile web apps. the simple examples could be shaking the device to undo the action, tilting the device to advance to the next or a previous page, gesturing towards camera to cause certain action.
Although movements such as shaking, tilting, gesturing towards, seem to be easy to perform for the person who does not have disability, however, the same movements are difficult or impossible to perform for the certain group of users. Let us understand this with some scenarios how difficult it is when the actions are associated with either user or device motions
- If the device is mounted to the wheelchair, it is not possible for the wheelchair user to shake or tilt the device to perform action
- If the user is having motor disability, neither it is possible to move the device to perform action nor it is possible to gesturing towards camera to perform action
- If the user is having tremors, user can accidently perform unintended actions that are related to device motion (such as shaking/tilting). As a result, it is not easy for those users to use the device smoothly.
- Even users who do not have disabilities, but their hands are occupied, it is not possible for those users to move the device to perform action
In a nutshell, associating actions/functionalities with the certain movements pose problems/challenges to some group of users.
WCAG 2.1 introduces the new checkpoint called “2.5.4: motion actuation” to address the mentioned problems. This success Criterion states that 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. To put this simpler if there is any user or device motion to perform action;
- Authors must provide the user interface control as an alternative to perform the same action. The below are the examples
- after inputting text at the text field, user must shake the device to undo the action. the cancel button is provided beside the text field to do the same action
- user must shake the device to roll the dice in the app. Control is provided to roll the dice
- user can tilt the device to advance to next and previous pages. the controls are provided to do the same action
- Authors must provide the settings to disable or turn off those user or device motions to prevent the accidental activations.
When the authors follow the above mentioned 2 points, the design is going to be inclusive and all the users including people with disabilities can perform the actions (related to movements) with not only the device or user movements but also with the simple tab or touch.
Complementary info on 2.5.4: motion actuation
This checkpoint is mostly applicable for the mobile devices and motion actuation things are built in the few native apps, but We rarely find motion actuation instances in the mobile websites.
There are exceptions to this success criterion.
- If the user motion or device motion is part of the accessibility feature, then it is an exception case. For example; eye gazing technology uses eye movements to access the computer, and this is an exception because it is assistive technology for the certain group of people with disabilities.
- If the device motion or user motion is an essential activity and disabling it or turning it off invalidates the entire thing then it is an exception. For example; A pedometer that relies on device motion to count steps is an example of such an essential activity.