NonLinear width and height are required
<NonLinear> missing required width or height attributes
Short answer
<NonLinear> overlays need both width and height so the player can size and place the unit. Missing either attribute usually makes the overlay fail or get ignored.
The `width` and `height` attributes on `<NonLinear>` (inside `<NonLinearAds>`) are required across all VAST versions — 2.0 through 4.2 and 4.3. They tell the player how much space to reserve and which rendition to select. A `<NonLinear>` element without both attributes will typically be ignored or cause layout failures. In VAST 4.2, the spec explicitly lists `width` and `height` as required attributes of the `<NonLinear>` element structure inside `<NonLinearAds>`.
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 2.0 and later (all versions).
How to fix
Add width and height attributes to every <NonLinear> element inside <NonLinearAds> — for example width="480" height="70". Both attributes are required by the IAB VAST spec from version 2.0 through 4.2 and 4.3. Without them most players will ignore or misrender the overlay.
Invalid
<NonLinearAds>
<!-- ❌ width and height attributes are missing -->
<NonLinear>
<StaticResource creativeType="image/gif">
<![CDATA[https://example.com/overlay.gif]]>
</StaticResource>
</NonLinear>
</NonLinearAds>Valid
<NonLinearAds>
<!-- ✅ width and height are present -->
<NonLinear width="480" height="70">
<StaticResource creativeType="image/gif">
<![CDATA[https://example.com/overlay.gif]]>
</StaticResource>
</NonLinear>
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