Understanding VPAID and VAST: What’s the Difference?

Video ads have grown tremendously over the past years and are poised to continue the trend. The latest report by Statista declared that advertisers would spend $104.87 billion in the US this year.

With video ads becoming increasingly popular, it is no wonder there are large debates about VPAID vs. VAST ad tags. Which is best for video ads? What’s the difference between them?

In this post, I’ll try to explain why these two standards have taken off in the digital advertising world and how they’re actually different from one another and give insight into which may be best for your business.

An Overview of Video Ad Standards

VAST and VPAID are video ad-serving protocols, meaning there are different rules on how a video ad should be delivered to the user. IAB (Interactive Advertising Bureau) framed the protocols to ensure the industry players have a standard way to interpret, deliver, and measure video ad campaigns.

Moreover, VAST and VPAID are not mutually exclusive. For the delivery of video ads, you will be using VAST in every case. The addition of VPAID is just the addition of new features to the already existing VAST framework. Let’s dive into the differences. Shall we?

What Is VAST?

VAST stands for Video Ad Serving Template. It helps with the communication between the ad server and the video player on the website.

Before the arrival of VAST, the ads had to be custom programmed according to the video players of the publishers, which hampered the ability to scale up video ad serving. 

VAST Tags: A Technical Outlook

VAST tags are the foundation of an online video ad service, but understanding the technical details behind them is important for publishers looking to optimize their ad budgets. Let's understand the underlying processes of VAST tags, explore definitions, available versions, and consider its limitations.

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How VAST Tags Work?

VAST tags are a three-step process:

1. VAST Request
   The video player initiates the process by sending a request to the ad server, requesting a VAST tag. This request typically includes information about the viewer and the video content being played.
2. VAST Inline Response
   Upon receiving the request, the ad server responds with an inline response containing the VAST tag itself. This tag is an XML document that outlines everything the video player needs to know about the ad, including:some text
   
   1. Ad media file: The location of the video ad file (usually an MP4 or WebM).
   2. Ad format: Whether it's a pre-roll, mid-roll, or post-roll ad.
   3. Tracking URLs: URLs that track ad impressions, clicks, and other events.
   4. Creative assets: Additional elements like companion banners or companion creatives.
3. Tracking URLs Pinged
   Once the ad plays as instructed by the VAST tag, the video player pings the specified tracking URLs to register ad impressions and other relevant actions.

Versions of VAST Tags

The IAB has continuously improved the VAST standard over time. Here's a quick rundown of the current versions:

It's important to note that VAST tags are backward compatible, ensuring a smooth flow within the ad-serving ecosystem.

Limitations of VAST Tags

While VAST tags are a powerful tool, they do have some limitations:

1. Complexity
   Understanding and working with VAST tags can be complex, especially for beginners.
2. Standardization Issues
   Although standardized, slight variations in implementation between ad servers and video players can sometimes lead to errors.
3. Limited Targeting Capabilities
   VAST tags themselves offer limited built-in targeting options. It requires additional layers like OpenRTB for more granular audience targeting.

Despite these limitations, VAST tags remain the basis of online video ad serving. Their standardized approach ensures smooth communication between ad servers and video players, ultimately enabling a seamless video ad experience for viewers. Want to know more? Here’s our detailed VAST guide.

What Is VPAID?

VPAID (Video Player Ad-Serving Interface Definition) was an early IAB standard created to enable executable, interactive video ad experiences beyond what traditional VAST media files allowed. However, as of 2025, VPAID is officially deprecated by the IAB Tech Lab and is no longer recommended for new integrations.

The deprecation is driven by several structural limitations that became increasingly problematic as programmatic video expanded across mobile, CTV, and server-side ad insertion (SSAI) environments:

• VPAID relies on executing JavaScript inside the publisher’s player, creating security and performance risks.
• It performs inconsistently across mobile apps and connected TV platforms, where JavaScript execution is restricted or unsupported.
• It conflicts with modern SSAI workflows, which are now the default for premium video publishers.

As a result, the industry has transitioned to newer, purpose-built standards:

• SIMID (Secure Interactive Media Interface Definition) for interactive ad experiences
• OMID (Open Measurement Interface Definition) for standardized viewability and verification

For publishers and programmatic leaders, VPAID should be considered a legacy technology and avoided in future-facing video ad stacks.

Interactive and Measurement Standards Used in 2025

VPAID versions are no longer actively developed or maintained. Instead, the IAB Tech Lab and the broader programmatic ecosystem now rely on SIMID and OMID, which were designed to solve the exact challenges VPAID could not scale to address.

SIMID (Secure Interactive Media Interface Definition)

SIMID enables rich interactive ad experiences while preserving publisher control of the video player. Interactive logic runs in a secure sandbox separate from media playback, making it compatible with web, mobile, and CTV environments.

OMID (Open Measurement Interface Definition)

OMID provides a standardized framework for viewability, verification, and fraud measurement across devices and platforms. It allows measurement vendors to collect consistent signals without requiring executable ad code.

For publishers, this shift improves:

• Platform stability
• Security posture
• Compatibility with SSAI and CTV monetization

SIMID replaces VPAID for interactivity, and OMID replaces VPAID for measurement.

How VAST Works with Modern Interactive and Measurement Standards

VAST acts as the foundational delivery layer that integrates with SIMID and OMID to support interactive and measurable video advertising at scale.

• VAST defines what ad to play, when to play it, and how tracking URLs are fired.
• SIMID enables interactive elements such as clickable overlays, menus, or dynamic CTAs without taking control away from the publisher’s player.
  OMID standardizes measurement, allowing advertisers and verification partners to evaluate viewability and engagement consistently across environments.

For publishers and programmatic leaders, this architecture ensures:

• Full compatibility with SSAI and CTV
• Improved performance and security
  Compliance with industry measurement standards

The modern video ad stack is VAST + SIMID + OMID. 

VPAID should not be used for new integrations, as it is deprecated and unsupported in many modern video environments.