vastlint
VAST-2.0-inline-adsystem

VAST-2.0-inline-adsystem

<InLine> must contain <AdSystem>

ErrorRequired fieldsIAB VAST 2.0 §2.3VAST 2.0 and later (all versions)

Short answer

<AdSystem> identifies the ad server that created the response. It is required inside every <InLine> and <Wrapper>. Omitting it violates the VAST spec and may cause auction-level tracking failures.

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

Add <AdSystem version="1.0">Your Ad Server Name</AdSystem> as a child of <InLine>.

Invalid

<InLine>
  <AdTitle>My Ad</AdTitle>
  <!-- missing AdSystem -->
</InLine>

Valid

<InLine>
  <AdSystem version="1.0">My Ad Server</AdSystem>
  <AdTitle>My Ad</AdTitle>
</InLine>
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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-root-has-ad-or-error<VAST> must contain at least one <Ad> or <Error>VAST-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-adtitle<InLine> must contain <AdTitle>VAST-2.0-inline-impression<InLine> must contain at least one <Impression>