2.3.1 Three Flashes or Below Threshold
Conformance level: A
Criterion released in WCAG version: 2.0
Official description of the success criterion
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.
What to do?
Do not include content that flashes more than three times in one second.
The flash size should not be too large. The flashing area should occupy less than 25% of any 10-degree visual field on the screen.
Red flashing is more likely to cause seizures. Especially when combined with high contrast.
Why is it important?
Prevents seizures in users with photosensitive epilepsy.
Common pitfalls
While with websites it's not a common practice to include flashing content, this effect might occur due to a problem with JavaScript or CSS. In those cases, multiple flashes might happen during a page load.