Accessibility
No more than three flashes a second
Never flash full-frame contrast more than three times in any second.
Takeaways
- Three flashes a second at most.
- No alternating full-frame black and white.
- No flashing saturated red.
- Change an element, not the ground.
What it means
Rapid flashing can trigger seizures in people with photosensitive epilepsy, so this is a hard limit and not a style choice. Avoid alternating full-frame black and white, avoid flashing saturated red, and change one element on a constant ground instead.
In a RasanAI film
The render gate measures flashes in the finished film (photosensitivity-flash) and fails it above the limit. Flash bursts vary one element on a locked layout and keep the luminance change small.
Origins and sources
WCAG 2.3.1, Three Flashes or Below Threshold (Success Criterion, level A). Ofcom's broadcast guidance sets a similar limit. Read the source.