Techniques for WCAG 2.0

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


Applies to any technology

This technique relates to:


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:

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.



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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