Web pages do not contain anything that flashes more than three times in any one second period.
Testing & RemediationHow to test: Navigate to any page that contains flashing content. While the content flashes, say “A and B and C”. This generally equals 3 vocalizations per second. If the content flashes faster that you saying “A and B and C”, this success criterion will fail. You can also use a tool to help test this, such as the PEAT (Photosensitive Epilepsy Analysis Tool). It is Windows only but can be installed on a dual-boot Mac. How to remediate: Remove any content that flashes more than 3 times in any 1 second period.
Questions and Answers
Most of the time animated gifs will be accessible. There should be a few things to keep in mind though to ensure this remains true. For example, ask yourself if there is another way that the message can be communicated. Would a still image do? If not, think about providing an alternative or some way that users can forgo the animation. A useful tool when checking your gifs for accessibility may be this Photosensitive Epilepsy Analysis Tool. The thought behind this is that you can make sure the animation won't trigger seizures in people who are sensitive to them.
This question depends on a number of factors including size of site, desired level of conformance, your developer's understanding of accessibility techniques, etc. Accessible Web is here to help. Reach out and we can discuss your site specifically.