13.7 On each web page, are sudden changes in brightness or blinking used correctly?

Test 1 (13.7.1)

1. Find in the document content which flashes or causes flash effects of the animated image, video (see note) or animation type (<img>, <svg>, <canvas>, <embed>, <object> or <video> elements).
2. For all content that flashes or causes flash effects, check that
   • either the frequency of the effect is less than or equal to 3 per second;
   • or the total surface area is less than or equal to 21824 pixels.
3. If this is the case for each content item that flashes or causes flash effects, the test is validated.

Note: assessing this criterion can be complex. When the effect is managed by a script or using CSS, analysis of the code is sufficient. The PEAT tool can be used to analyse videos in .avi format, for example. An example of a video that caused epileptic seizures can be found here: London 2012 Olympics Seizure.

Test 2 (13.7.2)

1. Find in the document the content that flashes or causes flash effects using a script.
2. For each content item that flashes or causes flash effects, check that
   • either the frequency of the effect is less than or equal to 3 per second;
   • or the total surface area is less than or equal to 21824 pixels.
3. If this is the case for each content item that flashes or causes flash effects, the test is validated.

Test 3 (13.7.3)

1. Find content in the document that flashes or causes flash effects using CSS animation.
2. For each piece of content that flashes or causes flash effects, check that
   • either the frequency of the effect is less than or equal to 3 per second;
   • or the total surface area is less than or equal to 21824 pixels.
3. If this is the case for each content item that flashes or causes flash effects, the test is validated.