Accessibility and Spatial Patterns (MDN Web Docs)

MDN’s guide to visual/spatial patterns — stripes and other repeating textures — that can trigger physical symptoms independent of motion or flashing.

License: CC BY-SA 2.5+ (Mozilla Contributors).

Key points

Stripe patterns are a seizure risk on their own, independent of motion. Five or more light-dark stripe pairs — parallel, radial, curved, or straight — can trigger a photosensitive seizure through visual-cortex “gamma oscillations,” even in a completely static image.
A static, unchanging pattern gets a looser threshold (eight pairs) than one that’s animating, oscillating, or flashing, since it’s inherently less provocative.
Higher luminance contrast within a pattern raises the risk — the same contrast that makes a striped pattern look perceptually “sharp” is what makes it more provocative.
Local padding and surrounding context affect a pattern’s perceived risk, not just its own contrast ratio — WCAG’s contrast math doesn’t account for this by itself.