Illustration of flashing lights with a warning sign
Image description: A red warning sign in front of a variety of chaotic, colorful shapes that represent flashing lights.

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Why This is Important

Flashing lights can induce seizures for people with epilepsy. Avoiding them reduces the chance of a medical emergency.

Flashing lights can also cause pain or discomfort for people who are sensitive to light or be distracting to people with ADHD, Autism, or other cognitive disorders. This includes sirens, strobe lights, and other visual flashing effects.

This references WCAG criteria 2.3.1 Three Flashes or Below Threshold (Level A) and 2.3.2 Three Flashes (Level AAA).

How to Implement This

Do not use flashing lights

According to WCAG, this refers to any lights that flash more than 3 times per second. Red lights are particularly triggering and should be avoided.

Learn more from the Epilepsy Society.

Provide a content warning

Example of content warning for flashing lights before playing a video
Image description: a video player showing an orange screen with a black play button and black text that says, "Warning: flashing lights. Press play to continue." A purple drop shadow with black stripes is in the background.

If displaying flashing lights is unavoidable, e.g. if it's video recording of an art installation or a concert performance, provide a content warning that is highly noticeable and allows for the user to exit or close the potentially triggering content.

Most social media platforms automatically play videos and do not include a way to add warning on the platform. If the video includes flashing lights, I recommend adding a 5-second title slide to the beginning of the video as well as a warning in the caption.

Interesting further reading

How to Test This

Manually go through the content and see if there are any flashing lights that could be potentially triggering (lights should not pose any harm to the tester).

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