Blinking and flashing animation can be problematic for people with cognitive concerns such as Attention Deficit Hyperactivity Disorder (ADHD). Additionally, certain kinds of motion can be a trigger for Vestibular disorders, epilepsy, and migraine and Scotopic sensitivity. The prefers-reduced-motion media query enables providing an experience with fewer animations and transitions to users who have set their operating system's accessibility preferences to reduce motion.

Also, this method of switching animation off according to the user's preference can also benefit users with low battery or low-end phones or computers.

no-preference

Indicates that the user has made no preference known to the system.

reduce

Indicates that user has notified the system that they prefer an interface that minimizes the amount of movement or animation, preferably to the point where all non-essential movement is removed.

This example has an annoying animation unless you turn on Reduce Motion in your accessibility preferences.

HTML

<div class="animation">animated box</div>

CSS

.animation {
  animation: vibrate 0.3s linear infinite both;
}

@media (prefers-reduced-motion: reduce) {
  .animation {
    animation: none;
  }
}

The value of prefers-reduced-motion is reduce, not "none". Users are not expecting no animation, such as could be set with * {animation: none !important;}. Rather, they expect motion animation triggered by interaction to be disabled, unless the animation is essential to the functionality or the information being conveyed (see WCAG: Animation from Interactions).

• Designing With Reduced Motion For Motion Sensitivities