Techniques for WCAG 2.0

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G15: Ensuring that content does not violate the general flash threshold or red flash threshold


Applies to any technology

This technique relates to:


The purpose of this technique 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.



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

  1. determine (with or without instruments) that there are no more than three flashes (6 transitions) of any kind in any one second period

    Note: If there are three flashes, check that the Light/Dark status at the end of the 1-second period is the same as at the start.


  2. determine that flashing is greater than 50 hz OR

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

Expected Results