VAST-4.2-icon-fallback-image-width-height
VAST-4.2-icon-fallback-image-width-height
<IconClickFallbackImage> should have width and height attributes
WarningAmbiguousIAB VAST 4.2 §2.4.5VAST 4.2 and 4.3
Short answer
<IconClickFallbackImage> (added in VAST 4.2) should carry width and height attributes so the player knows the dimensions of the fallback image before fetching it.
Why this matters in production
This rule is a strong risk signal. Tags with this issue often still parse, but they become brittle across SDKs, SSAI resolvers, and CTV environments. Ambiguous rules matter because undefined behavior shifts between vendors. Fixing them reduces the chance that two standards-compliant systems interpret the same tag differently. Affected scope: VAST 4.2 and 4.3.
How to fix
Add width and height attributes to <IconClickFallbackImage> so the player knows the dimensions before fetching.
Check your VAST tag for
VAST-4.2-icon-fallback-image-width-height and other issues instantly.Validate a tag →Other Ambiguous rules
VAST-3.0-progress-offset<Tracking event="progress"> requires an offset attributeVAST-3.0-icon-attrsIcon missing recommended attributes (program/width/height/position)VAST-2.0-nonlinear-dimensions<NonLinear> missing required width or height attributesVAST-2.0-companion-dimensions<Companion> missing width or heightVAST-4.0-wrapper-clickthrough<ClickThrough> inside Wrapper <VideoClicks> was removed in VAST 4.0 (re-allowed in 4.2)VAST-2.0-linear-tracking-quartiles<Linear> has no standard quartile tracking events — measurement system receives no signal