Table of Contents

    A page must not contain content that flashes more than three times a second. This ensures that people with conditions like photosensitive Epilepsy are protected from harmful seizures.

    Accessibility Requirements for 2.3.1 Three flashes or below (A)

    • Content does not flash more than three times a second.

    Common mistakes for 2.3.1 Three flashes or below (A)

    • Content flashes at more than three times a second.

    Techniques for 2.3.1 Three flashes or below (A)

    Each numbered item in this section represents a technique or combination of techniques that the WCAG Working Group deems sufficient for meeting this Success Criterion. However, it is not necessary to use these particular techniques. For information on using other techniques, see Understanding Techniques for WCAG Success Criteria, particularly the “Other Techniques” section.

    Common Failures for 2.3.1 Three flashes or below (A)

    • The following are common mistakes that are considered failures of Success Criterion 2.3.1 by the WCAG Working Group

    FAQs for Three flashes or below

    What is the purpose of testing for flashing?

    The intent of this criterion is to ensure that flicker that violates the flash thresholds is not caused by the content itself. For example, the content could contain a video clip or animated image of a series of strobe flashes, or close-ups of rapid-fire explosions.

    Why blinking flashing content should be avoided?

    Some content with flashing, blinking, flickering or rapidly changing colors can cause seizures in susceptible individuals.

    What are the exceptions for this guideline ?

    There’s one exception to this guideline based on the size of the flashing content, but I recommend you ignore it and just don’t let anything flash more than three times per second.
    “the combined area of flashes occurring concurrently occupies no more than a total of .006 steradians within any 10 degree visual field on the screen (25% of any 10 degree visual field on the screen) at typical viewing distance.”

    Related to Three flashes or below (A)

    Useful resources for 2.3.1 Three flashes or below (A)

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