VAST-2.0-root-element
VAST-2.0-root-element
Root element must be <VAST>
ErrorRequired fieldsIAB VAST 2.0 §2VAST 2.0 and later (all versions)
Short answer
The top-level element of a VAST document must be named <VAST>. Any other root element name — including a byte-order mark, an XML declaration mishap, or a wrapper element like <response> — will cause all players to reject the tag entirely.
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. 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 2.0 and later (all versions).
How to fix
Rename the root element to <VAST>.
Invalid
<VastResponse version="4.0">
<Ad id="1">…</Ad>
</VastResponse>Valid
<VAST version="4.0">
<Ad id="1">…</Ad>
</VAST>Check your VAST tag for
VAST-2.0-root-element and other issues instantly.Open the VAST tag validator →Other Required fields rules
VAST-2.0-root-version<VAST> must have a version attributeVAST-2.0-root-version-valueVAST version attribute must be a recognised version stringVAST-4.0-wrapper-root-error<VAST> root contains both <Ad> and <Error> elements (invalid per VAST 4.0)VAST-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>