What is the difference between VPAID and VAST?

VAST (Video Ad Serving Template) is an XML standard that describes a video ad: where to fetch the media, what tracking pixels to fire, and how to render the creative. VPAID (Video Player-Ad Interface Definition) is a JavaScript API specification that runs inside the player and was delivered via a VAST tag. VAST is the container; VPAID was an executable layer inside it. VPAID is now deprecated.

Is VPAID part of VAST?

Not exactly. VPAID is a separate IAB standard from VAST. A VAST tag can reference a VPAID creative by setting apiFramework="VPAID" on a MediaFile element. The VAST tag provides the delivery and tracking scaffolding; the VPAID JavaScript unit handles interactivity. They work together but are specified independently.

Can I use VPAID and VAST together?

Technically yes — legacy VAST 2.0 and 3.0 tags still reference VPAID via MediaFile apiFramework="VPAID". But VPAID is officially deprecated by the IAB Tech Lab and blocked by most CTV platforms and SSAI environments. You should migrate to SIMID for interactivity and OMID for measurement.

SIMID (Secure Interactive Media Interface Definition) replaces VPAID for rich interactive ad experiences. It uses a sandboxed iframe and postMessage instead of shared JavaScript execution. OMID (Open Measurement SDK) replaces VPAID's ad verification and viewability use cases. Both are referenced from VAST 4.x tags.

Why is VPAID blocked on CTV?

VPAID requires a browser JavaScript runtime. CTV devices use native media players with no browser context. SSAI stitches ads at the server where no JavaScript can run. SIMID solves this by running in an isolated iframe that CTV players can spawn without exposing the host environment.

VPAID vs VAST: what's the difference?

Short answer: VAST is the XML delivery standard — it describes the ad, where to fetch media, and which tracking pixels to fire. VPAID was a JavaScript API that ran inside the player and was referenced from a VAST tag. They are different standards that work together. VPAID is now deprecated; SIMID and OMID are its replacements.

Working with a VAST tag that uses VPAID?

Validate it to surface the deprecation warning and see what needs to change before it fails on CTV or in an SSAI environment.

Validate a tag →VPAID migration guide →

What VAST does

VAST (Video Ad Serving Template) is an XML document returned by an ad server. It tells the video player:

Where to fetch the video creative (the <MediaFile> URLs)
Which tracking pixels to fire (impressions, quartile events, clicks)
How to handle wrapper chains and ad pods
What companion ads to display alongside the video

VAST does not execute code. It is a declarative description of an ad. The current version is VAST 4.3, with a 2024 CTV Addendum for streaming environments.

What VPAID does

VPAID (Video Player-Ad Interface Definition) is a separate JavaScript API standard. A VPAID ad unit is a .js file that the player downloads and executes. The player calls into a standardised VPAID API (initAd(), startAd(), etc.) and the ad unit responds with events.

VPAID enabled capabilities VAST alone could not provide:

Interactive overlays, expandable panels, surveys, and mini-games
Precise viewability measurement (because the script ran in the player context)
Rich engagement metrics beyond standard tracking pixels

How they work together in a VAST tag

A VPAID creative is delivered via VAST. The VAST tag contains a <MediaFile> with apiFramework="VPAID" instead of a normal video URL:

<!-- VPAID delivered via VAST -->
<MediaFile delivery="progressive"
           type="application/javascript"
           apiFramework="VPAID"
           width="640"
           height="360">
  <![CDATA[https://adserver.example.com/creative.js]]>
</MediaFile>

The player fetches the VAST XML, sees apiFramework="VPAID", loads the JavaScript file, and hands control to the VPAID unit for the duration of the ad.

Side-by-side comparison

Property	VAST	VPAID
Format	XML document	JavaScript file + API contract
Role	Ad delivery & tracking container	Interactive executable layer
Executes code?	No	Yes — in the player's JS context
CTV support	Yes (native player reads XML)	No (no browser JS runtime)
SSAI support	Yes	No (server-side stitching, no JS runtime)
Current status	Active — VAST 4.3 is current	Deprecated (VPAID 2.0 was final version)
Replacement	—	SIMID (interactivity), OMID (measurement)

Why VPAID is deprecated

Three fundamental problems ended VPAID:

Security: VPAID ran in the same JavaScript context as the publisher's page. A malicious creative had full DOM access — a vector for ad fraud, data theft, and malware distribution.
CTV and SSAI incompatibility: Neither native CTV players nor server-side ad insertion have a browser JavaScript runtime. VPAID simply cannot execute in these environments, which now represent the majority of premium video inventory.
Latency: Because the VPAID script controlled media loading, the video asset could not be pre-buffered. Every impression paid a startup-latency penalty.

What replaced VPAID

VPAID use case	Replacement standard	How it works
Interactive overlays, expandable creatives	SIMID 1.2	Sandboxed iframe + postMessage; player retains media control
Viewability & verification measurement	OMID (Open Measurement SDK)	Separate SDK integrated by the player; no creative-side JS access

SIMID is referenced in VAST 4.x via the <InteractiveCreativeFile apiFramework="SIMID"> element alongside a normal video <MediaFile>. The player pre-buffers the video and loads the SIMID iframe separately — solving both the latency and the security problem.

Migrating from VPAID

If you are maintaining VAST tags that still reference VPAID:

Validate the tag — VASTlint will flag apiFramework="VPAID" on any <MediaFile> with rule VAST-2.0-vpaid.
Determine which VPAID use case applies: interactivity (→ SIMID) or measurement (→ OMID).
Follow the VPAID to SIMID migration guide for step-by-step XML changes and creative requirements.

Validate a VAST tag now to surface VPAID deprecation warnings and other delivery issues.Validate a tag →