Content that flashes or flickers can trigger seizures in users with photosensitive epilepsy. Developers, content creators, and video producers must be mindful of this accessibility concern and take steps to prevent flashing content in their digital materials.
Why this matters
Flashing content can trigger seizures in people with photosensitive epilepsy. This is one of the most critical accessibility requirements because the consequences can be immediate and physical. WCAG treats this as a Level A requirement, the most fundamental level of web accessibility.
Techniques
The best approach to handling flashing and flickering content is to avoid it entirely. However, if flashing content must be included, it is critical to follow accessibility guidelines. The general rule is that content should not flash more than 3 times per second, as flashing above this threshold can trigger seizures.
- WCAG 2.3.1 (Level A): Allows flashing if the flashes are dim and occur in a small area, provided a precise mathematical formula is met
- WCAG 2.3.2 (Level AAA): Forbids any flashing content entirely
Testing Tools
The Trace Center provides the PEAT tool for measuring seizure risk from flashing content. Note that this tool may not be actively maintained. When in doubt, assume your content may flash and eliminate it to ensure complete accessibility.
What To Do If You Have Flashing Content
- Remove or replace the flashing content entirely
- Reduce the flash rate below 3 flashes per second
- Ensure flashes are small in area and dim in intensity
- Provide clear warnings before flashing content appears
- Allow users to opt out of or disable flashing content
UGA-Specific Guidance
If you have questions or need guidance on flashing content, contact the Digital Accessibility Services (DASH) Team for accessibility consultation. For web-specific questions, contact EITS Web Services.
WCAG Criteria
- WCAG 2.3.1 Three Flashes or Below Threshold (Level A)
- WCAG 2.3.2 Three Flashes (Level AAA)
Getting help
If you have questions or need assistance, the Digital Accessibility Services Hub (DASH) is available to support colleges, schools, and administrative units as they build sustainable accessibility practices.
- Contact DASH at [email protected] for consultations, training, or technical assistance.
Accessibility is a shared responsibility, and every step you take makes UGA’s digital environment more inclusive.