GIFs should not cause the screen to blink |
WAI / WCAG 1.0 Priority 2 checkpoint 7.2
Issue Description The page contains images that might cause blinking on the screen. If this is the case, it is best to modify or remove them.
How to check Check if the image causes blinking (i.e. a constant on/off behavior of part of the screen) that does not stop and that cannot be stopped by the website visitor. If so, modify the image so that no blinking occurs, or so that it blinks a couple of times and then comes to rest.
Issue Explanation The image causes blinking and the user of the browser will in no way be able to stop this on/off behavior. This blinking behavior is very distracting to the eye, and will make it very difficult to concentrate on the task of reading the information on the page, or filling in the form contained on the page.

The consequences will be even more significant for users that suffer from cognitive disorders, as they will have a very hard time concentrating on the page content. Consider also users of screen magnifiers who may read a small portion of the page that overlaps with the blinking content. In these cases, a large part of the magnified screen will blink; again making it very hard for these users to concentrate on the task at hand.

Consider that, in a sense, everyone is cognitively disabled when under stress. For example, when buying an e-ticket for a flight from a kiosk in a very noisy and crowded airport, with a long line of people waiting for the same kiosk, most people will be unable to fully concentrate on the task. A blinking element in the page will not help the user to complete the purchase.