Operable / 2.3 Seizures and Physical Reactions
2.3.1Three Flashes or Below Threshold
Level ADo not include content that flashes more than three times per second, unless the flashes stay below the general and red flash thresholds. This prevents triggering photosensitive seizures, and the rule applies to any content on the page -- not just video, but also animations and flashing ads.
Note
A detailed commentary for this success criterion is not yet available. In the meantime, this page lists related patterns, techniques, and links to the normative sources.
Related Techniques
Specific implementation techniques for meeting this success criterion. This site doesn't include the full text, so follow the links to the original W3C documents.
Sufficient Techniques(3)
- G15: Using a tool to ensure that content does not violate the general flash threshold or red flash threshold(opens in a new tab)waic.jp(opens in a new tab)
- G19: Ensuring that no component of the content flashes more than three times in any 1-second period(opens in a new tab)waic.jp(opens in a new tab)
- G176: Keeping the flashing area small enough(opens in a new tab)waic.jp(opens in a new tab)
Normative References
- Success Criterion 2.3.1 Three Flashes or Below Threshold — WCAG 2.2(opens in a new tab)The normative requirement text.
- Understanding Three Flashes or Below Threshold — W3C(opens in a new tab)Official guidance on intent, examples, and techniques.