What is a VAST tag?

Still confused by VAST tags in TV ad tech?

When it comes to delivering captivating and immersive ad experiences on connected TV (CTV), one key element plays a pivotal role: VAST tags. These unassuming snippets of code are responsible for the seamless delivery of CTV creative that captivates viewers and drives engagement.

If you're a CTV advertiser, understanding the significance of VAST tags and how they contribute to the success of your campaigns is crucial. We’ll unravel the mysteries surrounding VAST tags and shed light on what CTV advertisers need to know about this integral component of their creative delivery strategy.

What is a VAST tag?

When CTV advertisers finish crafting their creative, they need a way to send the finished ad to platforms and publishers. This is where the VAST tag comes in.

A video ad serving template (VAST) tag is an ad script, or piece of code, generated by an ad server that allows video players and ad servers to communicate and exchange data with one another. Video players use VAST tags to understand specific information about an ad, allowing the video player to display the ad on the publisher’s platform properly.

There are many elements within a VAST tag. The most important ones to know include:

• Media file: This is the advertiser’s ad creative. It may contain various encodings for a specific creative so that the publisher or player can choose the best one to deliver based on the detected bandwidth of the audience.
• Video format: This specifies the format of the ad creative. Video formats can include linear, non-linear, skippable linear, companion ads, and more.
• Tracking URL: This tracks viewer behavior while interacting with video content. Events typically tracked using pixels include video start, 25%, 50%, and 75% video completes, and ad clicks.

VAST tag examples

What exactly does a VAST tag look like? If you’ve worked with HTML, the example below will look familiar.

To help break down what this all means, take a look at the numbers to the left-hand side — we’ve broken down what these snippets of code mean below.

1. Besides creative, VAST templates also contain information about tracking. TrackingEvents show advertisers if an ad has played successfully, how long it played for, and if it played successfully.
2. This portion of the code allows to the player to choose the right bitrate to download. It also contains the MediaFiles element, which describes the video to the player. Here, we can see that the video is an .mp4.
3. The VideoClicks element allows advertisers to interact with users who click on the ad. For instance, advertisers can redirect users to a different URI or track the click event.

Tip: Curious about what the latest version of VAST tags offers? The IAB has released a comprehensive guide for every VAST tag iteration.

How do VAST tags work?

How exactly does a VAST tag work? At a high level, here are the steps that take place when a VAST tag is used.

1. When a viewer watches a show on their CTV device, it triggers the video player to call the publisher ad server during an ad break. Here, the appropriate ad to be served is determined.
2. The publisher ad server hands the relevant ad back to the video player. At this point, the video player knows what ad to play, but it doesn’t know how to play it. What ad creative should the video player use?
3. The publisher ad server makes a VAST request. In other words, the publisher ad server will request instructions on how to play the appropriate ad — such as what creative to play and where the ad should be displayed within the video player’s interface.
4. The creative ad server receives the request and generates a VAST response. It contains specific details about the ad to be played, such as the media file URL, tracking URLs, and more.
5. The publisher ad server sends the VAST response back to the ad player. The CTV app or player receives the ad response and parses the VAST XML document, extracting the necessary information to fetch the relevant .mp4 movie file and play the video ad.

Tip: A huge problem in the industry is non-specificity. When advertisers refer to an ad server, they can mean a variety of things. Here, we refer to the publisher ad server and the third-party ad server (or creative ad server). The creative ad server is mostly responsible for determining which creative to serve, delivering it to the requestor, and counting.

Do VAST tags operate the same in connected TV as they do in display advertising? Not necessarily. In the connected TV space, it's not uncommon for a publisher to request to fill multiple ad break slots. For instance, if an ad pod has three thirty-second ad slots to fill, they may try to fetch all three ads at once.

This is very different from how video works in the desktop world, where every single ad slot makes a real-time call for a video ad when it needs it — in other words, it doesn't pre-fetch anything.

What are the benefits of VAST tags?

VAST tags have come a long way since their introduction in 2008. Some of their benefits include:

• It facilitates communication between ad servers and video players: VAST tags provide a standardized format for delivering video ads, making it easier for ad networks, publishers, and media players to understand and process the ad information. This standardization eliminates the need for custom integrations and allows for seamless interoperability across different platforms and devices.
• It saves time and money: Before 2008, video advertising was largely non-standardized. VAST was created as a way to solve this problem. Adhering to VAST standards allows publishers to seamlessly receive and display ads from different sources without the need for extensive modifications or troubleshooting. This eliminates the need for time-consuming ad format conversions or manual adjustments, saving publishers valuable resources.
• The barrier to entry is low: Numerous online tools and software solutions offer VAST tag generators and templates. These tools simplify the process of creating VAST ad tags by providing user-friendly interfaces where you can input the required parameters, such as video URL, tracking URLs, durations, and click-through URLs. The generators then generate the corresponding VAST tags, eliminating the need for manual coding.

VAST tag tips

• Avoid manual XML creation unless necessary, as errors are common. Instead, use platforms like Google Ad Manager or third-party tools.
• Validate tags with IAB-compliant tools to ensure compliance and fix formatting issues.
• Double-check for typos in URLs, durations, or tracking pixels.
• Generate unique tags per website.
• Test multiple formats (e.g., inline, companion, overlays) to identify top performers.
• Balance ad saturation by monitoring clicks/views.
• Compare ad formats (e.g., pre-roll vs. mid-roll) to identify engagement patterns.
• Pair ads with complementary video content to maintain user engagement.

Leveraging the Power of VAST Tags for CTV Advertising Success

With this information, you now better understand what the CTV ad delivery process looks like under the hood. For advertisers, understanding technical processes like these can take their CTV campaigns to the next level.

VAST tags are one piece of the ad tech puzzle, though. The connected TV advertising ecosystem is incredibly complex, and there’s much to learn. Ready to take your knowledge to the next level? Check out our guide to connected TV to learn even more about this growing space.