WCAG 2.0 · Level A · Operable
2.3.1 Three Flashes or Below Threshold
Manual verification
How to validate 2.3.1 by hand
Check for flashes that exceed the general and red-flash thresholds in any one-second period.
Start with the extension result
Reopen the reported URL and reproduce the same state (for example, after expanding a menu or submitting a form). Use the result’s Highlight action when available, or its affected-element details and CSS selector, to find the reported content. Apply the checks below to that content and its context. If the element or state has changed, rescan and record that difference before deciding whether the finding still applies.
- Inspect video, animation, transitions, and user-triggered effects for repeated flashes in a one-second interval.
- Use a reliable flash-analysis method or frame-by-frame measurement to evaluate flash frequency, area, and luminance/color changes.
- For a failing sequence, determine whether it is below the general flash and red-flash thresholds or below the specified screen-area limit.
Evidence to record
Record the clip/frame range, flashes per second, affected screen area, luminance change, and result of the threshold analysis.
Scope and exceptions
Visual spot-checking is not enough to establish flash safety. The criterion permits content below defined thresholds; apply the specified technical test and exceptions.
Record the review outcome
- Confirmed: the recorded evidence shows the requirement is not met in the tested page state, and no applicable exception explains it.
- Not reproduced: the reported issue is absent in the current state. Record the URL, state, and affected element you checked; this does not prove other pages or states conform.
- Needs more review: evidence is incomplete, the content requires human judgment, or an exception is uncertain. Record what remains to be checked instead of treating it as a pass.