Wrapper response
A Wrapper redirects the player to another VAST endpoint.
Wrappers chain. Players cap depth — usually at five.
Schema
A Wrapper carries a VASTAdTagURI and may declare its
own tracking, viewability, and verification metadata. The player
fetches the URI, resolves the next response, and merges trackers
from every wrapper it traversed.
<!-- VAST 4.3 wrapper, abbreviated -->
<Ad id="123">
<Wrapper followAdditionalWrappers="true" allowMultipleAds="false">
<AdSystem>example-ssp</AdSystem>
<VASTAdTagURI><![CDATA[https://upstream.example/vast.xml]]></VASTAdTagURI>
<Impression><![CDATA[https://t.example/imp?id=123]]></Impression>
<Creatives><Creative><Linear><TrackingEvents>
<Tracking event="complete"><![CDATA[https://t.example/cmp]]></Tracking>
</TrackingEvents></Linear></Creative></Creatives>
</Wrapper>
</Ad>
Common pitfall.
followAdditionalWrappers="false" on a wrapper means the
chain stops here, not that this wrapper is the last. Players that
read the field on the wrong node will silently truncate ad pods.
Tracking semantics
A wrapper's tracking events are additive. When the player resolves
the chain to an InLine ad, every Tracking URL declared
in every wrapper traversed must fire on the matching event in the
InLine creative. Players that dedupe by URL silently drop legitimate
analytics.