Level ASince WCAG 2.0
2.3.1 Three Flashes or Below Threshold
Guideline 2.3: Seizures and Physical Reactions – Nothing flashes or moves in a way that can make people ill.
What does the rule require?
Nothing flashes more than three times per second – or the flashing is small and dim enough to stay below the thresholds. Strong flashing can trigger epileptic seizures – this can be life-threatening.
How to get it right
Avoid flash and strobe effects. Check videos with an analysis tool such as PEAT.
Who benefits most?
- People with epilepsy
Official wording
This page explains the rule in simple words. Only the original W3C text is normative.
- “Understanding Three Flashes or Below Threshold” at W3C (external site)
- Techniques in the WCAG Quick Reference (external site)