Nothing on a webpage should flash more than three times in a second.

What you need to know

• The terms “flashing” and “blinking” can mean the same thing. WCAG distinguishes flashing as content that can cause a seizure. Blinking refers to content that can be a distraction. The two can be the same if blinking occurs faster than three times per second.

What you need to do

• Limit or eliminate any flashing content.
• The point here is to severely restrict flashing content. Although there are exceptions that provide for automatic content, make your website as static as possible by default, with options to activate helpful automatic content.

Reference

Read the full explanation of success criterion 2.3.1 on W3.org.

Related Resource

Check out “Flashing Accessibility Requirements” from the U.S. Access Board for more information about this success criterion.