WCAG 3.0 is an active W3C Working Draft in development by the AGWG. Requirements, assertions, the conformance model and reporting tiers are still being developed and may change. The latest published draft is the 10 September 2026 Working Draft; this site follows the editors’ draft, which also includes exploratory provisions.
A single large change of contrast counts too: content must not swing from light to dark, or dark to light, by more than 4.5:1 across more than 30% of the viewport. Loading a new page and essential flashes are excluded.
Why It Matters
A single full-screen flash can trigger seizures and can cause pain or after-images for people with light sensitivity, migraine or eye conditions - the harm does not require a repeating flash.
Design content without large changes of contrast. For example, when a menu with a light background is opened, it opens over a light background. Videos do not go from a dark to light background in less than a second.
This is a new provision for a big, intense, single on/off flash. This is reported as a trigger by group members, but we need data on this, and a definition that includes size/intensity to avoid including non-triggers such as menus.
This provision relies on the color contrast algorithm in WCAG 2. When the algorithm is updated for WCAG 3, the contrast metric will also be updated.
W3C Threads on This Provision
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Content does not include a change of contrast (over 4.5:1) going from light to dark (or dark to light) of more than 30% of the visible content area (viewport).
:::except-when
- A new page/view is loaded.
- The flash is essential.
:::
:::ednote
This is a new provision for a big, intense, single on/off flash. This is reported as a trigger by group members, but we need data on this, and a definition that includes size/intensity to avoid including non-triggers such as menus.
:::
:::ednote
This provision relies on the color contrast algorithm in WCAG 2. When the algorithm is updated for WCAG 3, the contrast metric will also be updated.
:::