Understanding WCAG SC 2.3.1 Three Flashes or Below Threshold

2.3.1 Three Flashes or Below Threshold: Web pages do not contain anything that flashes more than three times in any one second period, or the flash is below the general flash and red flash thresholds. (Level A)
Note: Since any content that does not meet this success criterion can interfere with a user’s ability to use the whole page, all content on the Web page (whether it is used to meet other success criteria or not) must meet this success criterion.
Three Flashes or Below Threshold Transcript
Hello everyone, today we’re going to give you an introduction to three flashes or below threshold. We’re also going to talk about its requirements, the benefited types, failure scenarios, a test case, and how we can fix them.Comic series, cartoon series, children’s shows, online and video games, and ads often carry contents that flash more than three times in any one second. While this pleases and adds more fun to the viewing experience, it pushes a lot of people, including children, to experience a photoepileptic seizure. This is even more dangerous when there is a red flash more than three times within a second. Based on research, WCAG mandates that any content that flashes must either not exceed three times in any one second or must be below the general or red threshold.
Now, let’s see who benefits from this. For users with photosensitive seizures, note that this type of disability is invisible. Nobody will know unless it happens in front of us or they tell us. This makes flashing content much more ominous to be handled.
Now, let’s look at some failure scenarios. A web page contains a video where a rapid-fire explosion occurs, and more than three flashes are shown in a second. It occupies a major real estate of the screen. A web page has a welcome video where a cat welcomes the users, and there is a bright light bulb on its head that blinks more than three times in a second at the center of the page.
Let’s see how we can test them. If your web page has flashing content, it is important to test for flashing requirements using the Trace Center Photosensitive Epilepsy Analysis Tool (PEAT).
Let’s see how we can fix them. One can ensure that there are no flashing contents as much as possible. When such contents are available, one can ensure that they do not flash more than three times in a second. One can also ensure that such contents occur at 1/4 of the screen. One of the best practices is to provide a mechanism globally to turn off the flashes across the site.
This is the end of the video. Thank you for joining. If you like the video, do like and subscribe.
This success criterion conveys that there mustn’t be any flashing content that flashes more than 3 times per second. In the past, flashing content has caused Epileptic seizure in users. So it is a best practice to avoid the flashing content totally & achieve the same design & functionality using other development techniques.
How do I know if the flash meets the criterion?
PEAT-Photosensitive Epilepsy Analysis Tool can be used to determine if the flashing content passes this check point.
Exception
An exception has been provided for this check point so that designers/developers who want to use flashing content can use with caution. Here is the exception:
The combined area of flashes occurring concurrently occupies no more than a total of .006 steradians within any 10 degree visual field on the screen (25% of any 10 degree visual field on the screen) at typical viewing distance.
Nice write up Raghava ….
Thanks for your article! Is this same criteria applicable to mobile apps as well?
Hello Amanda,
Yes, this is applicable to mobile. WCAG is not specific to any technology. it is technology agnostic.
Hello Amanda,
yes, it is applicable to mobile too.