VASTlint
Validate
VAST-4.1-adservingid-present

InLine needs AdServingId in VAST 4.1+

<InLine> must contain <AdServingId> (VAST 4.1+)

ErrorRequired fieldsIAB VAST 4.1 §2.3VAST 4.1, 4.2, and 4.3

Short answer

<AdServingId> is required on <InLine> from VAST 4.1. It is an opaque unique id the ad server assigns so impressions and errors can be deduplicated.

Starting with VAST 4.1, `<AdServingId>` is a required element inside `<InLine>`. It carries an opaque unique identifier assigned by the ad server for event deduplication and reconciliation.

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 4.1, 4.2, and 4.3.

How to fix

Add <AdServingId>unique-id-per-response</AdServingId> inside <InLine>, generating a fresh UUID for every ad response.

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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-adsystem<InLine> must contain <AdSystem>VAST-2.0-inline-adtitle<InLine> must contain <AdTitle>