Background

§1194.21(k) of Section 508 states that:

"Software shall not use flashing or blinking text, objects, or other elements having a flash or blink frequency greater than 2 Hz and lower than 55 Hz."

Flashing or blinking frequencies between 2 Hz and 55 Hz can trigger seizures in people who have photosensitive epilepsy. The likelihood of triggering a seizure is significantly increased if the intensity of the flash is high and if it falls within a certain frequency range. Because of this problem, developers must limit the flash or blink rates of all screen items. The requirement outlined in this provision applies primarily to software and web development; however, it also applies to hardware for flashing lights and controls. Common examples of frequently used flashing objects are “Hot” or “New” words.

The purpose of this provision is to ensure that flashing or blinking elements do not utilize frequency rates that may trigger adverse affects in people with photosensitive epilepsy.

Testing your application for conformance, and remediating issues identified, are relatively simple procedures.

Select the Next button to find out how to assess whether your application conforms to this provision.