vastlint
VAST-4.0-wrapper-clickthrough

VAST-4.0-wrapper-clickthrough

<ClickThrough> inside Wrapper <VideoClicks> was removed in VAST 4.0 (re-allowed in 4.2)

WarningAmbiguousIAB VAST 4.0 §2.5 / VAST 4.2 §2.5VAST 4.0, 4.1, 4.2, and 4.3

Short answer

VAST 4.0 removed <ClickThrough> from wrapper <VideoClicks> but VAST 4.2 re-introduced it. If you are targeting 4.0 or 4.1 players specifically, this element will be ignored.

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 4.0, 4.1, 4.2, and 4.3.

How to fix

If targeting VAST 4.0 or 4.1 specifically, remove <ClickThrough> from wrapper <VideoClicks>; in VAST 4.2+ it is allowed again.

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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-4.2-icon-fallback-image-width-height<IconClickFallbackImage> should have width and height attributesVAST-2.0-linear-tracking-quartiles<Linear> has no standard quartile tracking events — measurement system receives no signal