Epilepsy & Seizures

Around 3% of people with epilepsy have photosensitive epilepsy, where seizures can be triggered by flashing or strobing light, patterns, or rapidly changing visuals. Vestibular disorders, which affect balance and spatial orientation, can be worsened by motion and parallax effects. Both are reasons to design moving content carefully and give users control over it.

WCAG (Web Content Accessibility Guidelines) addresses this directly. Success Criterion 2.3.1 requires nothing flashes more than three times per second above defined luminance thresholds. Success Criterion 2.3.3 requires that motion triggered by interaction can be disabled, unless it's essential. The prefers-reduced-motion CSS media query lets you respond to the user's system setting automatically. If content might cross flash thresholds, check it with the Photosensitive Epilepsy Analysis Tool (PEAT) from the Trace Center.

Avoid flashing or strobing content. Use slow transitions rather than rapid motion. Respect prefers-reduced-motion. Give clear controls to pause or disable animation, and warn before any unavoidable flashing content.