What is a VAST Wrapper

VAST Wrapper Examples: A Complete Guide

VAST plays a crucial role in standardizing how video ads are delivered across different players and platforms. One of the key features of VAST is the VAST Wrapper, which allows ad servers to chain together multiple VAST responses before finally delivering the media file to the video player.

In this article, we'll explain what a VAST Wrapper is, why it's used in video advertising, and walk through detailed examples of how Wrappers work in practice. Whether you're an ad ops professional, developer, or advertiser, understanding Wrappers is critical to troubleshooting video ads and optimizing campaign delivery.

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What is a VAST Wrapper?

A VAST Wrapper is a type of VAST response that doesn't directly provide a media file (the video ad itself). Instead, it "wraps" another VAST tag by pointing the video player to a different ad server or VAST URL. This chaining can happen multiple times, creating what's known as Wrapper depth.

In simpler terms, a VAST Wrapper is like a redirect. Instead of providing the final video file, it forwards the player to another VAST response, which could be another Wrapper or the final InLine VAST (the response containing the actual video creative).

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Why Are VAST Wrappers Used?

VAST Wrappers are widely used in video advertising for several reasons:

• Ad Serving Flexibility: Wrappers allow advertisers, DSPs, and SSPs to pass control across multiple platforms before selecting the final ad.
• Tracking and Reporting: Each Wrapper can contain its own tracking pixels and events, ensuring all parties in the ad supply chain record impressions, clicks, and completions.
• Ad Waterfalling: If one ad server cannot deliver a creative, Wrappers can redirect to another tag, improving fill rate.
• Verification & Compliance: Wrappers allow verification vendors (e.g., MOAT, IAS, DoubleVerify) to insert tracking for viewability, fraud detection, and brand safety.

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Example 1: Simple VAST Wrapper

Below is a simple example of a VAST Wrapper that redirects to another VAST tag.

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<VAST version="4.2">
  <Ad id="12345">
    <Wrapper>
      <AdSystem version="1.0">AdServer A</AdSystem>
      <VASTAdTagURI><![CDATA[https://example.com/vast-response.xml]]></VASTAdTagURI>
      <Impression><![CDATA[https://tracker.example.com/impression]]></Impression>
      <Error><![CDATA[https://tracker.example.com/error]]></Error>
      <Creatives></Creatives>
      <TrackingEvents>
        <Tracking event="start"><![CDATA[https://tracker.example.com/start]]></Tracking>
      </TrackingEvents>
    </Wrapper>
  </Ad>
</VAST>

In this case: - The video player fetches this VAST tag. - It sees that it's a Wrapper, not an InLine creative. - The player then fetches the VASTAdTagURI, which points to another VAST response.

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Example 2: Multi-Layered VAST Wrappers

Sometimes, Wrappers can chain together multiple ad servers before resolving to the final ad. This is common in programmatic advertising, where DSPs, SSPs, and verification vendors are all involved.

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<VAST version="4.2">
  <Ad id="67890">
    <Wrapper>
      <AdSystem version="2.0">SSP Example</AdSystem>
      <VASTAdTagURI><![CDATA[https://dsp.example.com/vast-wrapper.xml]]></VASTAdTagURI>
      <Impression><![CDATA[https://ssp.example.com/impression]]></Impression>
      <Creatives></Creatives>
      <TrackingEvents>
        <Tracking event="complete"><![CDATA[https://ssp.example.com/complete]]></Tracking>
      </TrackingEvents>
    </Wrapper>
  </Ad>
</VAST>

That VASTAdTagURI may itself return another Wrapper (from the DSP), and eventually an InLine VAST with the actual video creative.

This multi-hop process ensures that: - Each platform (SSP, DSP, Advertiser) gets proper tracking credit. - Ads are dynamically selected in real time. - The final media file only loads once the Wrapper chain resolves.

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Best Practices for Handling VAST Wrappers

• Limit Wrapper Depth: Excessive Wrappers (e.g., 5+ redirects) can slow down playback and increase errors. Many players set a max depth (commonly 5).
• Validate Wrappers: Use a VAST testing tool to confirm Wrapper chains resolve correctly.
• Ensure Tracking Consistency: Make sure each Wrapper has valid tracking pixels to avoid discrepancies in reporting.
• Monitor Errors: Implement <Error> tracking to capture failed Wrapper resolutions.

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Conclusion

VAST Wrappers are an essential part of the digital video ad ecosystem, enabling flexibility, tracking, and compliance across multiple platforms. However, they can also introduce latency and complexity if overused. By understanding how Wrappers work and testing them properly, advertisers and developers can ensure smooth and effective video ad delivery.

If you want to test VAST Wrappers and debug Wrapper chains, try our wrapper example VAST test, built to validate and troubleshoot VAST tags efficiently.

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GitHub VAST Wrapper Sample Tag

AdMeIn has a range of sample tags available on GitHub to help you get started with VAST. Included is a VAST wrapper example: AdMeIn GitHub repository.