How Do You Check a Video for Flashing or Flickering Imagery?

Review strobe-like effects, rapid full-screen cuts, high-contrast alternating frames, saturated red flashes, game capture, stage lights and archival footage. A flash can come from source material you did not create. Mark the time range and examine it at playback speed; slowing the editor timeline alone may hide the actual rhythm. Ask whether the effect carries meaning or is merely decoration. Do not assume that a warning before a sequence makes an avoidable hazard acceptable.

The Web Content Accessibility Guidelines (WCAG) 2.2 web-content criterion 2.3.1 addresses flashes more than three times in one second unless they are below defined general or red-flash thresholds. That is a scoped standard, not a statement that any video with three or fewer flashes is safe for every viewer. Flash area, intensity and colour matter. Counting cuts by eye cannot measure the thresholds or certify a piece. If formal conformance matters, use an appropriate analysis method and the exact current criterion.

Remove a decorative strobe, use a slower transition, reduce the intensity or replace the shot. If a rapid effect is important to the work, consider an alternate cut and qualified testing before distribution. A game or concert creator may not control every captured light, but can still select or edit the passage. Do not present a numeric 'safe' setting for all screens and people. An artistic intention can remain while the avoidable flash is changed.

Effects can change after export, cropping or platform conversion, so check the actual file and intended playback. Document which sequence was revised and why, especially when another editor will make later versions. This is accessibility guidance, not medical advice about an individual's photosensitivity and not a legal certificate. The broader accessibility pass checks captions, text, audio and visual meaning; it cannot substitute for a flashing-specific assessment when one is needed.

The WCAG criterion is scoped to web content. This page does not declare a particular video safe for every viewer or provide a medical assessment.

• W3C: WCAG 2.2 flashing criterion
• W3C: Understanding flashing thresholds
• W3C WAI: media production