Some people with photosensitivity disorders may experience headaches or seizures when viewing content that flashes or has rapidly changing colors. Avoiding things that flash is one of the most important accessible design considerations because of the severity of the problem for people affected by it. The Trace Center’s Photosensitive Epilepsy Analysis Tool is helpful for testing content that might flash.
For sites that include a dark mode, it’s important to avoid flashes of unstyled dark mode screens in between page loads on slower connections.
People with vestibular disorders, vertigo, and other types of motion sensitivity may have problems with virtually all animation. We should respect browser settings to reduce motion by turning off animation.
Sound design is important for people with sensory processing issues. Twitter’s (now defunct) accessibility team did an extensive research project to make their sound effects less jarring or grating for people in this group.