Table of Contents
What is VAST? Brief History
In the digital advertising ecosystem, VAST is extremely valuable, with the VPAID ad format that automatically delivers interactive ads to a media player. However, providing causes definite challenges for publishers. For example, if the player doesn’t support the interactive format, the video ad may fail to display or load slowly. VPAID is also used for measurement and verification rather than for ad interactive delivery, as it was designed. The SIMID and OMID standards have recently replaced it.
Despite the drawbacks, VAST continues to improve as the digital media marketplace has become increasingly complex. VAST 4.3 solves several challenges, helping create an easy, productive workflow between partners.
Top VAST 4.3 Features
VAST 4.3 doesn’t reinvent video ad serving, but it significantly refines how ads are measured, verified, and delivered, especially in CTV and server-side environments. The update focuses on fixing long-standing gaps between how video ads are served and how they’re actually measured.
1. Improved Ad Verification Support
One of the biggest upgrades in VAST 4.3 is better alignment with ad verification and measurement workflows.
VAST 4.3 improves how verification resources are declared and passed, making it easier for platforms to integrate with OMID, measurement SDKs, and third-party verification vendors. This is especially critical in environments where JavaScript-based tracking is limited or unavailable.
Why it matters: Publishers and advertisers get more consistent fraud detection, viewability, and brand-safety reporting, without relying on fragile workarounds.
2. Stronger Support for Server-Side Ad Insertion (SSAI)
CTV and OTT continue to rely heavily on server-side ad insertion, where traditional client-side signals often disappear.
VAST 4.3 improves how impression, quartile, and completion events are defined and tracked in server-to-server setups. This reduces discrepancies between what the server logs and what advertisers see in reports.
Why it matters: More accurate measurement in SSAI environments means fewer disputes, cleaner reporting, and better trust between buyers and sellers.
3. More Reliable Measurement Signals
VAST 4.3 focuses on event consistency—ensuring that core events like impressions, starts, and completions are triggered and interpreted the same way across platforms.
This helps reduce ambiguity around:
- When an impression should fire
- How playback milestones are tracked
- How errors and fallbacks are handled
Why it matters: Cleaner signals improve attribution models, pacing logic, and optimization—especially for performance-driven video campaigns.
4. Better Error Handling and Debugging
Error reporting has been refined to provide more precise signals when something goes wrong in the ad delivery chain.
VAST 4.3 makes it easier to understand whether an issue occurred at the creative, player, network, or server level.
Why it matters: Faster troubleshooting, fewer silent failures, and better fill rates—especially in complex multi-hop programmatic setups.
5. Alignment with Modern Video Standards
VAST 4.3 continues to move closer to other IAB Tech Lab standards, including SIMID, OMID, and Open Measurement frameworks.
While VAST remains focused on ad delivery, this alignment ensures smoother interoperability with interactive creatives, measurement SDKs, and privacy-aware environments.
Why it matters: A more future-proof video stack that works across web, mobile, in-app, and CTV without custom logic for every environment.
For familiarization with all VAST 4.3 features, please, take a look at VAST 4.3 specification.
In 2023-2024, VAST 4.3 got several improvements:
- VAST Addendum for CTV 2024 – includes ACIF Support for Ad Registration, Icons to Support DSA, and updates relating to the need for higher resolution creative on larger screens
- VAST Addendum for attribution reporting – supports APIs that enable registering event URLs, includes attribute to identify URLs for potential attribution reporting.
Key Differences of VAST 4.3 Compared to 4.0
IAB Tech Lab added some additional changes and fixes to the VAST 4.3 over time. At the moment, the list of the latest updates includes the following:
- Fixed HTMLResource description & example
A “snippet” of HTML code to be inserted directly within the publisher’s HTML page code. - Creative Resource Files for Non-Video and Non-Audio
NonLinear ads, Companions, and Industry Icons are non-video and non-audio creative, so creative files are nested using elements that define the creative resource file provided: StaticResource, IFrameResource, and HTMLResource. - Fixed IconClickFallbackImage(s) references
The element is used to display information when an icon click occurs. - The VAST Terminology List was updated
- Added reference to “latest” macros list
New macros can be added without requiring a new VAST version at every change. The latest list is being maintained on the IAB Tech Lab’s VAST GitHub repository. - A new macro was added for [PLAYBACKMETHODS]. It indicates continuous play, so now users can watch content episodes one by one without any actions.
- Now one can include inline URI data for interactive creative files, for example when putting HTML instead of URL for retrieving files.
Why VAST 4.3 Matters Overall for Advertisers and Publishers
VAST 4.3 represents a meaningful step forward in how video ads are delivered, measured, and verified across today’s fragmented video ecosystem. Rather than introducing radical changes, the latest VAST 4+ updates focus on stability, transparency, and cross-platform compatibility – areas that matter most to both advertisers and publishers.
Below are the key takeaways from the latest VAST 4.3 updates and how they improve outcomes on both sides of the market.
Better User Experience and Playback Control
VAST 4.3 continues the shift toward a player-centric architecture, giving video players greater control over ad playback and user experience. This reduces unexpected behaviors and ensures ads behave consistently across environments.
Support for mezzanine files and stronger SSAI compatibility improves video quality and enables reliable ad delivery across a wider range of devices, including CTV, OTT, and mobile.
Result: higher-quality playback, fewer interruptions, and better viewer retention.
Higher-Quality and More Diverse Video Ads
The latest VAST updates expand support for interactive and audio ad formats, allowing buyers to deliver richer, more engaging creatives without sacrificing video quality.
Advertisers can also integrate multiple verification vendors through a single setup, making it easier to deploy interactive elements while maintaining brand safety and measurement standards.
Result: better creative flexibility for advertisers and more premium inventory for publishers.
A More Reliable Ad Delivery Process
VAST 4.3 improves the reliability of ad delivery by reducing errors and simplifying how creatives are served and tracked.
- Expanded macro support improves device recognition and targeting accuracy
- Clearer separation between media files and logic simplifies ad architecture
- Improved error handling reduces blank ads and failed impressions
- SIMID support enables interactive ads across web, mobile, OTT, and CTV
Result: cleaner delivery pipelines, higher fill rates, and fewer reporting disputes.
More Transparent and Actionable Reporting
With VAST 4.3, reporting becomes more consistent and transparent. Simplified tags and clearer creative tracking allow advertisers to better understand where and how ads are delivered, while publishers gain more control over their inventory and performance insights.
Result: better optimization decisions and stronger trust between buyers and sellers.
Advanced and Unified Ad Verification
VAST 4.3 strengthens alignment with Open Measurement (OMID), enabling a single verification setup to work across platforms and environments.
This allows advertisers to access multiple verification vendors without complex integrations, while publishers benefit from standardized, privacy-aware verification workflows.
Result: scalable, consistent verification across web, in-app, and CTV.
Additional Enhancements Worth Noting
- Macros are now managed independently on GitHub, reducing dependency on future VAST updates
- Inline data URI support enables interactive creatives to embed HTML directly, instead of relying on external file retrieval
These updates offer more flexibility for advanced creative and delivery use cases.
Industry Adoption and Transition
VAST has grown from a basic way to deliver video ads into one of the core standards of modern video advertising. As the industry moves toward CTV, OTT, SSAI, and privacy-first measurement, VAST is no longer just about serving ads; it helps maintain consistent, trustworthy delivery, measurement, and verification across the entire video ecosystem.
While everyone is waiting for the next big VAST update, VAST 4.3 already does the job. It’s a stable and practical standard that fits how video advertising works today. For companies focused on CTV and server-side delivery, supporting VAST 4.3 isn’t a “nice to have” anymore; it’s essential for running scalable, measurable, and reliable video campaigns.