Web Development
Web Developer Guidelines
Visual Design Recommendations

Checkpoint 9.3 - Core

Do not cause the screen to flicker or text to blink

WCAG 1.0 Priority 1

WCAG Guideline 7. Ensure user control of time-sensitive content changes.

Flickering or blinking text can be distracting for readers of the web page. Additionally, a flickering or flashing screen may cause seizures in users with photosensitive epilepsy. Seizures can be triggered by flickering or flashing in the 4 to 59 flashes per second (Hertz) range with a peak sensitivity at 20 flashes per second as well as quick changes from dark to light (like strobe lights).

Requirement

Do not use techniques on Departmental web sites that result in the screen flickering or text blinking.

Checking Tool

  • View the web pages in a browser to ensure that no images or other screen components cause flickering or blinking on the screen.
  • Internet Explorer - AIS toolbar: Tools > Simulations > Flickering Images Demo

Information Source

The original source of this information is located on the W3C web site  (www.w3.org/TR/WCAG10-TECHS/#tech-avoid-flicker)

 

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