VAST-4.0-wrapper-bool-attr
VAST-4.0-wrapper-bool-attr
<Wrapper> followAdditionalWrappers, allowMultipleAds and fallbackOnNoAd must be a boolean
WarningSchemaIAB VAST 4.0 XSDVAST 4.0, 4.1, 4.2, and 4.3
Short answer
Those three attributes are xs:boolean. Legal values are true, false, 1, and 0. Anything else is ignored or misread by 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. Schema violations tend to create parser disagreement. One system may recover while another drops the tag entirely, which is why these bugs often show up as environment-specific fill loss. Affected scope: VAST 4.0, 4.1, 4.2, and 4.3.
Check your VAST tag for
VAST-4.0-wrapper-bool-attr and other issues instantly.Open the VAST tag validator →Other Schema rules
VAST-2.0-text-only-elementText-only element contains a child elementVAST-2.0-unknown-attributeElement has an attribute not defined in the VAST specVAST-2.0-inline-unknown-child<InLine> contains an unrecognised child elementVAST-2.0-wrapper-unknown-child<Wrapper> contains an unrecognised child elementVAST-2.0-creatives-unknown-child<Creatives> may only contain <Creative> elementsVAST-2.0-creative-unknown-child<Creative> contains an unrecognised child elementVAST-2.0-linear-unknown-child<Linear> contains an unrecognised child elementVAST-2.0-trackingevents-unknown-child<TrackingEvents> may only contain <Tracking> elements