VAST-2.0-version-mismatch: Declared version does not match structural signals

Q: How do I fix VAST-2.0-version-mismatch?

Update the `version` attribute on ` ` to match the highest version your elements require — e.g. use `4.1` if you are using ` ` or ` ` text content.

Q: What does the VAST error "Declared version does not match structural signals" mean?

The `version` attribute on ` ` claims one version (e.g., `4.1`) but the document uses elements or attributes that only exist in a different version. This causes players to either ignore those elements or reject the tag.

VAST-2.0-version-mismatch

Declared version does not match structural signals

WarningConsistencyIAB VAST 2.0 §2.1VAST 2.0 and later (all versions)

Short answer

The version attribute on <VAST> claims one version (e.g., 4.1) but the document uses elements or attributes that only exist in a different version. This causes players to either ignore those elements or reject the tag.

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. Consistency rules catch documents that technically contain the right pieces but combine them in ways that produce conflicting signals for downstream systems. Affected scope: VAST 2.0 and later (all versions).

How to fix

Update the version attribute on <VAST> to match the highest version your elements require — e.g. use 4.1 if you are using <AdServingId> or <UniversalAdId> text content.

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Other Consistency rules

VAST-2.0-parse-errorXML parse error — document may be malformed VAST-2.0-duplicate-impressionDuplicate <Impression> URL within the same <Ad>

VAST-2.0-version-mismatch

Why this matters in production

Related docs

Other Consistency rules