VAST-2.0-nonlinear-unknown-child
VAST-2.0-nonlinear-unknown-child
<NonLinear> contains an unrecognised child element
ErrorSchemaIAB VAST 2.0 §2.4.3VAST 2.0 and later (all versions)
Short answer
<NonLinear> has a defined set of allowed children per the VAST schema.
Why this matters in production
This rule is usually a delivery blocker. Many players, SDKs, and ad servers will discard the response or skip the affected creative once this condition is hit. 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 2.0 and later (all versions).
How to fix
Remove the unrecognised element from <NonLinear>.
Check your VAST tag for
VAST-2.0-nonlinear-unknown-child and other issues instantly.Validate a tag →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