vastlint

CTV VAST errors: the failures that break streaming delivery

Short answer

CTV players are much less forgiving than desktop tooling. The failures that break streaming delivery most often are deprecated VPAID, deep wrapper chains, missing mezzanine source files, browser-only verification assumptions, and non-HTTPS media or tracking URLs.

Why this happens

Native TV players do not behave like browsers. They may not expose a JavaScript runtime to the ad, they often enforce stricter wrapper and timeout limits, and many SSAI or CTV trafficking workflows want a mezzanine source for transcoding. Tags that appear acceptable on desktop QA can still fail silently once they hit Roku, tvOS, webOS, Tizen, or Fire TV.

That is why CTV debugging has to be both structural and platform-aware. You need the rule result and the target environment in view at the same time.

Copyable fix example

<MediaFiles>
  <Mezzanine delivery="progressive" type="video/mp4" width="1920" height="1080">
    <![CDATA[https://cdn.example.com/ad-mezzanine.mp4]]>
  </Mezzanine>
  <MediaFile delivery="progressive" type="video/mp4" width="1280" height="720">
    <![CDATA[https://cdn.example.com/ad-720p.mp4]]>
  </MediaFile>
</MediaFiles>

<AdVerifications>
  <Verification vendor="example.com-omid">
    <JavaScriptResource apiFramework="omid" browserOptional="true">
      <![CDATA[https://cdn.example.com/omid.js]]>
    </JavaScriptResource>
  </Verification>
</AdVerifications>

VAST XML fragment only. This excerpt belongs inside a complete VAST document, so standalone validation will fail until it is wrapped in a full <VAST>response.

Exact rule pages

Use the right tool for this failure

If you already have the resolved XML, run a pure spec check. If you only have a live tag URL, test that endpoint first. If the failure happens in the wrapper chain, inspect each hop.

Validate this XML →Test this live URL →Inspect this wrapper chain →

Further reading