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Do flashing elements flash at a rate of less than 3 Hz?


Let’s not accidentally give anyone with photosensitive epilepsy seizures.

Why this matters

A seizure can cause muscle spasms, breathing problems, headaches, memory problems, and abnormal behavior. Seizures can be fatal.

In other words, this is one of the limited number of cases where what we put on the web could physically affect someone’s well-being, or kill them.

How to implement

Seizure disorders are complex. Read the following resources:

Be conscious of the fact that animation does not need to be produced by an animation application such as Photoshop or Flash. This test applies to animated SVG images and HTML elements that use JavaScript for animation as well. Any animation that changes the color of an element on the page rapidly or through certain color ranges (especially if it’s a large element) can cause issues.

How to test

Check the video or animated assets using the Trace Research & Development Center’s free Photosensitive Epilepsy Analysis Tool (PEAT) to identify risky material. (It’s a Windows application.)