WCAG 2.3.1:Three Flashes or Below Threshold

How to

• Avoid flashing content

  Do not use content that flashes or flickers more than three times per second. This mainly affects videos, animated images, GIFs, or interactive effects, for example, blinking warnings or rapidly changing colors. Any sudden change in color or contrast that occurs more than three times within one second counts as a “flash.”

  Example: An animation that switches between red and white may not change colors more than three times per second. If it does, it must be adjusted so that it runs more slowly.

  Since it is difficult to check this visually, the WCAG recommends using this tool to test flashing areas (Windows only).

  Technique(s):

  • G19: Ensuring that no component of the content flashes more than three times in any 1-second period
  

• Keep the flashing area small

  If you can’t get rid of the flashing, you must at least ensure that the area is tiny!

  The flashing area should occupy less than 25% of the central 10° field of vision so that the flashing is perceived less intensely. As a rule of thumb: with a screen width of 1024 pixels, this would be 148 × 148 pixels.

  The calculation can be found in WCAG Technique G176.

  Technique(s):

  • G176: Keeping the flashing area small enough