2.3.1: Three Flashes or Below Threshold

What it means

Web pages must not contain content that flashes more than three times per second, or flashes below general flash and red flash thresholds. Flashing content can trigger seizures in people with photosensitive epilepsy.

Applies to video, animations, and rapid strobe effects.

How to fix it

• Avoid strobe effects, rapid GIFs, and flashing alerts.
• Keep animation below three flashes per second if motion is essential.
• Test video and hero animations with a flash analysis tool.
• Replace flashing “NEW” badges with steady highlights.

Quick examples

• Good: A loading spinner rotates smoothly without rapid strobing.
• Bad: A error banner blinks red five times per second.
• Good: Video is edited to remove seizure-inducing flash sequences.
• Bad: A full-screen white/black flicker transition repeats during page load.