Techniques for WCAG 2.0

On this page:

-

# G15: Using a tool to ensure that content does not violate the general flash threshold or red flash threshold

## Applicability

Applies to any technology

This technique relates to:

- Success Criterion 2.3.1 (Three Flashes or Below Threshold)
  - How to Meet 2.3.1 (Three Flashes or Below Threshold)
  - Understanding Success Criterion 2.3.1 (Three Flashes or Below Threshold)

## Description

The purpose of testing for violations of the general and red flash thresholds is to allow people who have photosensitive seizures to view Web sites without encountering material that is likely to cause a seizure. Warnings can be provided but people may miss them and children may not be able to read or understand them. With this technique all material is checked and if it violates flash or red flash thresholds it is either not put on the site or it is modified so that it does not violate the thresholds.

Note 1: There are some simple tests that can be run for particular simple types of flashing. For example:

- If material flashes 3 times per second or less then the simple test in G19: Ensuring that no component of the content flashes more than three times in any 1-second period can be used.

- If material flashes in only one place on screen at a time and is quite small then the simple test in technique G176: Keeping the flashing area small enough can be used.

Note 2: For all other types, a tool is needed to keep track of all the factors and apply them to the video on a time-continuous basis.

## Examples

- An animation of a thunderstorm shows six flashes of lightning. The flashes are so fast and large that the general flash threshold is violated when tested with a flash analysis tool. The animation is modified to create a short pause after each pair of lightning flashes. After the changes are made, the animation does not violate the general flash threshold.

## Resources

Resources are for information purposes only, no endorsement implied.

- Harding FPA Web Site

- Trace Center Photosensitive Epilepsy Analysis Tool (PEAT)

## Related Techniques

- G19: Ensuring that no component of the content flashes more than three times in any 1-second period
- G176: Keeping the flashing area small enough

## Tests

### Procedure

Check to see to see that content does not violate the general flash and/or red flash threshold

1. use a tool that to determine that neither the General Flash nor Red Flash threshold were exceeded

### Expected Results

- Check #1 is true.

- Top
- Contents
- Intro
- Previous: Technique G14
- Next: Technique G17