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For some people, flashing light on a screen can trigger a seizure. This is one place where an animation choice becomes a safety choice. ⚠️

The risk has a name: photosensitive epilepsy. Bright, rapid flashes are the classic trigger for people who live with it.

WCAG sets a clear line. Nothing should flash more than three times in any one second, or it must stay below a small safe area.

A flash is a pair of opposite changes: bright to dark and back. Three of those bright-dark cycles within a second crosses the threshold.

Saturated red flashes carry their own warning in WCAG, because deep red transitions are especially likely to provoke a seizure.

A tiny flashing dot is low risk; a flashing full screen is high risk. The rule cares about how much of the view is involved.

The danger is not just GIFs. Video with strobe effects, explosions, or rapid cuts can flash past the limit without you noticing.

Even a frantic loading spinner or a blinking alert can flash too fast. Keep any repeating pulse slow and gentle.

When in doubt, measure. The free PEAT tool from the Trace Center analyzes media for flash that breaks the threshold.

The easiest fix is to avoid flashing at all. If an effect even feels strobe-like, slow it down well under three flashes per second.

If flashing media is truly unavoidable, give a clear warning first so a sensitive viewer can choose to look away.

What is the safe flashing limit under WCAG?

Keep anything flashing under three flashes per second, watch saturated red, and check video with PEAT. Safer is slower. ✅