What is a VAST Tag, and How to Create & Validate It?

Video advertising is one of the fastest-growing forms of digital marketing, and behind the scenes, VAST tags make it possible to deliver video ads smoothly across platforms. If you’re a marketer, publisher, or advertiser working with video campaigns, understanding VAST tags is essential.

This guide will explain what a VAST tag is, why it matters, how it works, and the steps to create and validate it.

What is a VAST Tag?

VAST (Video Ad Serving Template) is a standardized XML script developed by the Interactive Advertising Bureau (IAB). Its main purpose is to create a universal format for delivering video ads between ad servers and video players.

Simply put, a VAST tag is a piece of code that provides instructions to a video player. It tells the player:

Where the ad file is located.
How the ad should be displayed.
Which tracking events (impressions, clicks, completions) need to be recorded.

Whenever you see a video ad on YouTube, in a mobile app, or on an OTT platform, a VAST tag is what allows that ad to play and report performance data.

Why Are VAST Tags Important?

VAST tags play a crucial role in programmatic video advertising. Here’s why they are so valuable:

Consistency – They standardize ad delivery across different platforms and devices.
Analytics – They help advertisers measure impressions, clicks, completion rates, and engagement.
Flexibility – Publishers can integrate them with multiple ad networks and servers.
Cross-Device Coverage – Ads run seamlessly on desktops, mobiles, smart TVs, and apps.
Revenue Growth – Proper tracking ensures publishers are paid for ad views and clicks.

How Does a VAST Tag Work?

The working process of a VAST tag is straightforward:

Video Player Request – When a user clicks play, the player requests an ad.
Ad Server Response – The ad server sends back the VAST XML tag.
Ad Display – The video player reads the XML and loads the ad file.
Event Tracking – As the ad plays, the VAST tag fires tracking pixels for impressions, clicks, and completions.

This ensures accurate reporting for both advertisers and publishers.

Structure of a VAST Tag

A VAST tag is written in XML. Below is a simplified example:

<VAST version="4.0">
  <Ad id="001">
    <InLine>
      <AdSystem>Example Ad Server</AdSystem>
      <AdTitle>Demo Video Ad</AdTitle>
      <Impression><![CDATA[https://tracking.com/impression]]></Impression>
      <Creatives>
        <Creative>
          <Linear>
            <Duration>00:00:15</Duration>
            <MediaFiles>
              <MediaFile delivery="progressive" type="video/mp4" width="640" height="360">
                <![CDATA[https://example.com/ad.mp4]]>
              </MediaFile>
            </MediaFiles>
          </Linear>
        </Creative>
      </Creatives>
    </InLine>
  </Ad>
</VAST>

This XML defines the ad details, such as its title, duration, impression tracker, and media file link.

How to Create a VAST Tag?

You can create a VAST tag through an ad server or a video ad platform. The process typically includes:

Select an Ad Server – Platforms like Google Ad Manager or SpringServe allow VAST tag creation.
Upload Your Video Ad – Add your MP4, WebM, or compatible video file.
Add Tracking Links – Insert impression, click, and completion trackers.
Generate the XML Tag – The server automatically creates a unique VAST tag.
Distribute the Tag – Share it with publishers or embed it into your video player.

How to Validate a VAST Tag?

Before running a live campaign, it’s critical to test your VAST tag. Here’s how:

Use VAST Testing Tools – Google’s VAST Inspector or third-party validators can check if the tag is functional.
Check the XML Code – Make sure the code is properly structured without missing elements.
Run Tests on Different Devices – Test playback on desktop browsers, mobile apps, and OTT platforms.
Verify Trackers – Ensure that impression and click tracking URLs fire correctly.
Compare Reports – Once live, compare ad server and publisher reports for accuracy.

Best Practices for VAST Tags

To avoid issues and maximize performance, follow these tips:

Use the latest IAB version (VAST 4.0 or higher).
Provide multiple media file formats for compatibility.
Test tags before launching campaigns.
Always use secure HTTPS links.
Keep the XML code clean and lightweight.

Common Problems with VAST Tags

Sometimes VAST tags don’t function as expected. Common issues include:

Ad not playing – Often caused by unsupported or missing video formats.
Broken tracking – Incorrect or inactive tracker URLs.
Player incompatibility – Some older players may not support VAST 4.0.
Slow loading – Large video files increase latency.

Conclusion

A VAST tag is the backbone of digital video advertising. It connects ad servers with video players, ensures ads display correctly, and tracks performance in real-time.

By knowing how to create, test, and validate a VAST tag, advertisers can run more effective campaigns, while publishers can maximize revenue without technical errors.

If you’re working in the world of video advertising, mastering VAST tags is not just helpful—it’s essential.

Article Categories:

Marketing & Advertising