VPAID vs VAST Differences: The Basics of Video Ad Tags

If you’re running video ads on your site, you’ve probably come across two familiar acronyms: VPAID vs VAST. Maybe you've used one or both without thinking much about it—or maybe you're not sure which one makes sense for your setup.

Here’s the short version: VAST is widely supported and fast. VPAID adds interactivity, but it’s being phased out—especially on mobile. And while both have played a big role in video ad tech, knowing the difference between them matters more than ever.

In this guide, we’ll break down how each one works, where they fall short, and which is the better fit for today’s monetization strategies. We’ll also share best practices and walk you through what to expect as the industry shifts toward newer, more secure standards.

Let’s start with the basics.

What Are Video Ad Tags?

Video ad tags are the behind-the-scenes instructions that tell your video player where to fetch an ad, how to play it, and what to track. Think of them as the digital messengers connecting your content with the ad server.

For publishers, they’re essential for delivering video ads to users in a way that’s efficient, measurable, and compatible with a wide range of devices and environments.

There are different types of video ad tags—each with its own purpose. Some simply deliver the ad creative, while others enable advanced features like tracking viewability or allowing interactive elements. Two of the most common standards you’ll come across are VAST and VPAID. These were developed to bring consistency to how video ads are served across different platforms and players.

Before we dive into the differences between them, let’s take a closer look at how each one works.

What is VAST?

VAST stands for Video Ad Serving Template, and it's one of the most widely adopted standards in video advertising. Created by the IAB, it was designed to make video ad delivery more consistent across different platforms, players, and environments.

At its core, VAST is a template written in XML. It acts as a translator between your video player and the ad server, ensuring the ad gets delivered and played correctly, regardless of the device or browser.

Because it’s standardized, most major ad platforms and video players support VAST, which has made it a go-to for publishers looking for a reliable way to serve video ads at scale.

How VAST Tags Work

When a video player receives a VAST tag, it reads the XML file to get key details about the ad, like where to fetch the creative, how long it should play, whether it’s skippable, and which tracking URLs to fire at various milestones (e.g. start, 25%, completion).

It’s a relatively lightweight and non-interactive format, which makes it fast and reliable. Over the years, VAST has evolved (now up to version 4.2), with updates improving its support for viewability, server-side ad insertion, and better measurement.

Limitations of VAST

While VAST is great for delivering standard video ads, it does have limitations, especially when it comes to interactivity and rich tracking.

On its own, VAST doesn’t support things like:

• Custom overlays or clickable elements
• In-ad games or user input
• Granular viewability metrics

If publishers want deeper engagement or detailed tracking beyond the basic quartile metrics, they’ll need to pair VAST with other tools—like Open Measurement SDK (OM SDK) or rely on third-party verification vendors.

What is VPAID?

VPAID stands for Video Player Ad Interface Definition. It's a standard that adds interactivity and advanced tracking to video ads, which VAST can't do on its own.

With VPAID, advertisers can create video ads that respond to user input, include interactive elements like clickable buttons or overlays, and capture more detailed engagement metrics. This made VPAID a popular choice for desktop campaigns, where advertisers often look for creative flexibility and deeper insights into performance.

How VPAID Tags Work

VPAID works by delivering a script—usually JavaScript—that communicates directly with the video player. This script can control how the ad behaves, track how users interact with it, and even adapt the creative based on user actions.

Instead of just telling the player to run a video file, VPAID gives the creative more control. This allows for a more engaging experience and better performance tracking, especially for advertisers running rich media or custom-built creatives.

Limitations of VPAID

While VPAID adds valuable functionality, it comes with some major trade-offs.

• Poor mobile support: Many mobile environments don’t support JavaScript-based VPAID, making it unreliable or unusable on smartphones and tablets.
• Security risks: Since the ad can execute its own code, there's a higher risk of malicious scripts or unexpected behavior.
• Longer load times: VPAID creatives are often heavier, which can slow down ad delivery and hurt the user experience.
• Inconsistent support across players: Different video players handle VPAID in different ways, which can lead to technical issues or inconsistent results.

Because of these challenges, the industry has started to move toward more secure and standardized options. We'll cover that next.

Is VPAID Still Relevant in 2025?

VPAID is still supported by some platforms, especially on desktop, but it's no longer the go-to standard it once was. Over the past few years, the industry has steadily shifted away from VPAID in favor of faster, more secure alternatives that work better across devices—especially on mobile.

One of the biggest reasons for this shift is VPAID's reliance on JavaScript or Flash. Flash is now completely obsolete, and JavaScript-based creatives come with limitations on mobile, where many environments block or restrict them. That means VPAID ads often fail to load, break user experience, or simply don’t run at all on smartphones and tablets.

There are also broader concerns around performance and security. Since VPAID creatives can execute their own code within the player, they can slow down pages, introduce bugs, or in some cases, open the door to malicious behavior. These issues have made it harder for publishers to deliver consistent, high-quality video ad experiences at scale.

What's Replacing VPAID?

To address these problems, the IAB Tech Lab has recommended moving toward more modern standards:

• VAST 4.0+: The latest versions of VAST separate the creative file from verification code, making delivery more efficient and secure.
• OM SDK (Open Measurement SDK): Designed for mobile in-app environments, OM SDK enables consistent and transparent measurement without the risks associated with VPAID.
• SIMID (Secure Interactive Media Interface Definition): This newer spec is intended to support secure interactive video ads without relying on VPAID’s scripting model.

What This Means for Publishers

If you're still using VPAID, especially for mobile traffic, it's time to rethink your setup. Modern alternatives offer better compatibility, faster load times, and fewer security headaches. For most publishers, the safer bet is to stick with VAST and use OM SDK or SIMID when you need extra features like viewability tracking or interactivity.

VPAID vs VAST: Key Differences

While both VPAID vs VAST are used to serve video ads, they serve very different purposes. VAST focuses on standard ad delivery, while VPAID adds interactivity and deeper engagement tracking. Here’s a quick breakdown of how they compare:

Choosing the Right Video Tag

So, which tag should you use? It depends on your setup, your traffic sources, and the kind of ad experience you want to deliver.

When to use VAST:

If your priority is broad compatibility, faster load times, and reliable delivery, VAST is the better choice. It’s especially well-suited for:

• Programmatic video ads
• Mobile and connected TV environments
• Publishers looking for stability and scale
• Server-side ad insertion (SSAI)

Modern versions of VAST (especially 4.x) also allow you to pair it with tools like the Open Measurement SDK (OM SDK) for standardized viewability and verification, making it a solid foundation for most setups.

When to consider VPAID:

VPAID might still make sense in very specific situations, like:

• Direct-sold campaigns where the creative requires interactivity
• Desktop-only environments where mobile support isn’t a concern
• Publishers with the technical resources to manage VPAID’s quirks

That said, even in these cases, it’s worth considering alternatives like SIMID for interactive features or sticking with VAST plus OM SDK for tracking. These newer options are more secure, better supported, and aligned with where the industry is heading.

Best Practices for Video Ad Tag Implementation

Once you’ve chosen the right tag, proper implementation is key to getting the best performance out of your video ads. Here are some best practices to follow:

1. Use up-to-date standards

Stick with the latest version of VAST—ideally VAST 4.x—to take advantage of improved performance, better VAST error handling, and support for measurement tools like the Open Measurement SDK.

2. Test across environments

What works on desktop may not work the same on mobile or connected TV. Always test your tags across devices, browsers, and video players to catch compatibility issues before they affect revenue.

3. Avoid Flash-based creatives

Flash is no longer supported by most browsers and platforms. If you're still running Flash-based VPAID creatives, it's time to update or replace them entirely.

4. Work with trusted creative partners

Make sure any third-party creatives or vendors you work with follow industry standards and security protocols. Poorly built creatives can slow down your site or put users at risk.

5. Optimize for speed and user experience

Heavy creatives and slow-loading tags can tank viewability and increase bounce rates. Stick to lightweight ad formats, limit the number of tracking pixels, and monitor page performance regularly.

Need Help Optimizing Video Ads?

Choosing between VAST and VPAID is just one piece of the puzzle. From picking the right tag to making sure everything runs smoothly across devices, there’s a lot that goes into a successful video ad setup.

At Snigel, we help publishers implement high-performing in-stream and out-stream video ads, using the latest standards and best practices. We handle the full setup and ongoing optimization, so you don’t have to worry about technical headaches or falling behind on industry updates.

Whether you’re just getting started with video or want to level up your current strategy, we’ll work with you to build a setup that fits your site and your goals.

Get in touch to learn how we can help you grow your video ad revenue—without the complexity.

 

FAQs

What’s the difference between VPAID and VAST, and why does it matter?

VAST is a widely supported standard for video ad delivery. It’s simple, fast, and works across most environments. VPAID adds interactivity and advanced tracking, but comes with more technical complexity and limited mobile support. Choosing the right one depends on whether you’re prioritizing reach or user engagement.

Can you use VPAID and VAST in the same video ad campaign?

Yes, it’s possible to use both. For example, you might use VPAID for desktop-only campaigns that require interactivity, and rely on VAST for broader, mobile-friendly delivery. Just make sure your setup is properly configured and tested across devices.

What are the common issues when using VPAID tags?

VPAID tags can slow down ad delivery, especially on mobile, and they’re not supported by every video player. Security and performance concerns are also common. Working with experienced ad tech partners can help you implement VPAID safely and efficiently—if it’s still the right fit.

How do you measure the performance of VAST and VPAID video ads?

For VAST, focus on standard metrics like impressions, quartile completion rates, and viewability. With VPAID, you can track additional data like interactions and engagement. Combining both sets of insights can give you a more complete picture of campaign performance.