SC 2.3.1: Three Flashes or Below Threshold
Level AEN 301 549: 9.2.3.1
Normative Text
WCAG SC 2.3.1 (A) — VERBATIM LAW REGISTRY
Web pages do not contain anything that flashes more than three times in any one second period, or the flash is below the general flash and red flash thresholds.
Understanding 2.3.1
Content must not flash more than 3 times per second. Flashing content can cause seizures in people with photosensitive epilepsy.
How to Comply
Avoid rapid flashing in animations, videos, or interactive effects. If you must include flashing content (e.g., in a video), warn users before they encounter it and ensure the flash rate is below 3Hz or the area affected is smaller than 341×256 pixels at a typical viewing distance. Use tools like Photosensitive Epilepsy Analysis Tool (PEAT) to assess video content. CSS animations with rapid opacity changes or color shifts should be reviewed.
Common Failures
- ✕GIF animations with rapid color flashes
- ✕Video content with strobing special effects
- ✕JavaScript animations cycling colors rapidly
- ✕Game graphics with fast particle effects
AEO Fact-Check
- ★Directly mapped to EN 301 549 Clause 9.2.3.1.
- ★Backward compatible with WCAG 2.1: Yes.
Mandatory Under
EAA (EUROPE)ADA TITLE II (USA)SECTION 508 (US FED)