VAST-4.0-wrapper-root-error
VAST-4.0-wrapper-root-error
<VAST> root contains both <Ad> and <Error> elements (invalid per VAST 4.0)
WarningRequired fieldsIAB VAST 4.0 §2.1VAST 4.0, 4.1, 4.2, and 4.3
Short answer
In VAST 4.0 and later, the <VAST> root must contain either <Ad> elements **or** a single <Error> element — not both. Mixing them violates the schema choice and may confuse players.
Why this matters in production
This rule is a strong risk signal. Tags with this issue often still parse, but they become brittle across SDKs, SSAI resolvers, and CTV environments. Required-field failures usually stop validation early because the platform cannot determine the basic shape of the ad, the creative metadata, or the mandatory tracking payload. Affected scope: VAST 4.0, 4.1, 4.2, and 4.3.
How to fix
Remove either all <Ad> elements or the <Error> element so only one type exists under <VAST>.
Check your VAST tag for
VAST-4.0-wrapper-root-error and other issues instantly.Open the VAST tag validator →Other Required fields rules
VAST-2.0-root-elementRoot element must be <VAST>VAST-2.0-root-version<VAST> must have a version attributeVAST-2.0-root-version-valueVAST version attribute must be a recognised version stringVAST-2.0-ad-has-inline-or-wrapperEach <Ad> must contain exactly one <InLine> or <Wrapper>VAST-2.0-inline-adsystem<InLine> must contain <AdSystem>VAST-2.0-inline-adtitle<InLine> must contain <AdTitle>VAST-2.0-inline-impression<InLine> must contain at least one <Impression>VAST-2.0-inline-creatives<InLine> must contain <Creatives> with at least one <Creative>