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( Operable / WCAG 2.3.1 )

Content flashes more than 3 times per second

This check maps to Three Flashes or Below Threshold. Use the guidance below to confirm the issue, understand who it affects and ship a fix.

Critical Level A WCAG 2.3.1 — Three Flashes or Below Threshold

What’s wrong

An animation or CSS effect causes content to flash more than three times per second.

Why it matters

Rapidly flashing content can trigger seizures in people with photosensitive epilepsy. This is a life-safety issue. Even below the seizure threshold, fast flashing causes severe discomfort and can trigger migraines. This is Level A — address it before anything else.

How to fix it

Remove or slow down any flashing animation to below 3 flashes per second. Always respect the user’s reduced motion preference.

Before 
@keyframes flash {
  0%, 100% { opacity: 1; }
  50% { opacity: 0; }
}
.alert {
  animation: flash 0.1s infinite;
}
After 
@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.6; }
}
.alert {
  animation: pulse 2s ease-in-out infinite;
}

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

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