VAST-4.1-mezzanine-width
VAST-4.1-mezzanine-width
<Mezzanine> missing required width attribute
ErrorRequired fieldsIAB VAST 4.1 §2.4.1VAST 4.1, 4.2, and 4.3
Short answer
<Mezzanine> requires a width attribute.
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 width with the pixel width of the mezzanine video to <Mezzanine>.
Check your VAST tag for
VAST-4.1-mezzanine-width and other issues instantly.Validate a tag →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>