For people who have epilepsy or other photosensitive seizure conditions, flashing material on a website can be problematic. These users might experience a seizure in response to flashing content.
This rule gives only a hint and requires manual verification.
According to WCAG 2.1, Success Criterion 2.3.1, items on a web page cannot flash more than three times in a single second or less frequently than the general and red flash thresholds. Its goal is to make the experience accessible for people who could be photosensitive or could have seizures.
How to fix it
- Anything that flashes more than three times per second shouldn’t be added to your website.
- Before submitting any videos or animations to your website, you can run them through the Trace Center’s Photosensitive Epilepsy Analysis Tool (PEAT) to see if they fit the requirements.
If the flashing content is below a specific size (that’s dependent on the viewport) it passes the criterion regardless of the flash threshold.
Accessibility, WCAG 2.1, Success Criterion 2.3.1 Three Flashes or Below Threshold, Level A