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

Important Information about Techniques

See Understanding Techniques for WCAG Success Criteria for important information about the usage of these informative techniques and how they relate to the normative WCAG 2.0 success criteria. The Applicability section explains the scope of the technique, and the presence of techniques for a specific technology does not imply that the technology can be used in all situations to create content that meets WCAG 2.0.


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 to determine that neither the General Flash nor Red Flash threshold were exceeded

Expected Results

If this is a sufficient technique for a success criterion, failing this test procedure does not necessarily mean that the success criterion has not been satisfied in some other way, only that this technique has not been successfully implemented and can not be used to claim conformance.