Photosensitive epilepsy and online content

People with photosensitive epilepsy may have seizures triggered by displays that flicker, flash, or blink.

This is particularly the case if the flash has a high intensity and is within certain frequency ranges.

Online, this often relates to the use of animated GIFs and videos.

What are the guidelines for producing safe content for people with photosensitive epilepsy?

The World Wide Web Consortium (W3C) is the international standards organisation for the internet. Their accessibility guidelines recommend that web content does not:

  • Contain anything that flashes more than 3 times in any 1 second period or
  • Flash below the general flash and red flash thresholds

They also suggest:

  • Reducing contrast for any flashing content
  • Avoiding fully saturated reds for any flashing content
  • Reducing the number of flashes even if they do not violate thresholds
  • Providing a way to stop any flashing content before it begins
  • Slowing down live material to avoid rapid flashes (as in flashbulbs)
  • Freezing the image momentarily if there are 3 flashes in 1 second
  • Dropping the contrast ratio if there are 3 flashes in 1 second
  • Allowing users to set a custom flash rate limit

If the user is not able to control the flickering, blinking and moving (this includes stopping the content from starting), then the effects should not be used.

Am I breaking the law by producing flashing content?

In many countries, such as the UK, it is illegal to discriminate against disabled people. This includes people with epilepsy.

If your content breaks the W3C good practice guide (above), then you should consider if there is a valid reason for it to do so. If there isn’t then you should edit your content to make sure it meets the W3C guidelines.

If you’re in the UK and you’re producing content for marketing or advertising, you must follow the Advertising Standards Authority rules.

If you’re in the UK and you are working in the public sector, then you need to make sure that your content complies with the Public Sector Bodies (Websites and Mobile Applications) (No. 2) Accessibility Regulations 2018.

The UK’s disability discrimination laws led to British TV regulators producing the ‘Guidance Note for Licensees on Flashing Images and Regular Patterns in Television’. Many online producers use their guidelines to check their content.

I have produced some content that flashes. Should I give a warning to users?

If you feel there’s a good reason why your content should break the W3C guidelines, then we strongly urge you to give a warning before the flashing starts. For example, on a video, the warning should be before the user starts to play the video.

If you don’t alert people with photosensitive epilepsy to flashing and someone has a seizure as a result of your content, you may be breaking the law.

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