2.3 Seizures and physical reactions

Like my last post, I'm going to cover the wider section and gloss over the subsections within it. This guideline says:

Do not design content in a way that is known to cause seizures or physical reactions.

I would like to hope that in 2021, people are aware that flashing lights can cause seizures for people with certain conditions. From personal experience of photosensitivity, they can also trigger migraines. Who knows what else? 

I would question why you would use flashing, given that this is known to be problematic but like the safety note on suppositories that tells you not to take them orally, you know someone is trying it.


I have to confess that I'm not the greatest fan of PowerPoint. I was a primary school teacher back in the day when it was all new and exciting. Y6 children (initially) were taught how to use PowerPoint and then gave endless presentations to their class, the school, the staff, different classes, etc. They made all the rookie errors, because we (the teachers) taught them too much about the different effects and not enough about appropriateness. 

We taught them how to change fonts and colours but didn't teach them about contrast. We taught them about animations and entrance/exit effects but didn't teach them about seizures. We taught them about experimentation and variety but not simplicity and consistency. 

The result was a class full of multicoloured winking, blinking, whizzing presentations that were enough to make anyone nauseous. It's nothing short of a miracle that more seizures didn't occur! And, post-teaching, I avoided PowerPoint like the plague.

Safety trumps pretty

Many people, like me, now avoid using every single animation and special effect, and go for subtle, clean and modern... but there might be situations where you want to use effects. The key is this:

Don't use anything that flashes, flickers, winks and blinks. Just don't. No matter how pretty it looks and how much you love it, if it could trigger a seizure for someone, that is just too much pretty. Their right to stay safe and well is bigger than anyone's need to show off their PowerPoint skills. 

If you must use them, you are going to need to learn even more advanced skills and provide a warning that the content contains flashing images and provide a way for the user to turn them off. I don't know how to do that. I don't need to know. I don't do flashing and flickering. 

Next time, we go back to stuff that I love! A huge block of guidelines about navigation. Can't wait!


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