vastlint

VAST 4.4: what to expect in the next IAB VAST version

VAST 4.3 was released in December 2022. The most recent official update from IAB Tech Lab is the VAST CTV Addendum 2024 (July 2024), which added ACIF support, DSA icon compliance, and higher-resolution creative guidance as backwards-compatible extensions rather than a new version number. A VAST 4.4 spec revision is expected to formalize these extensions and address accumulated open issues from the IAB Tech Lab GitHub repository.

Status: VAST 4.4 has not been officially announced as of April 2026. The content below is based on the VAST CTV Addendum 2024, open IAB working group issues, and the broader IAB Tech Lab 2026 roadmap. vastlint will validate VAST 4.4 tags as soon as the spec is published.

What VAST 4.3 added (the immediate predecessor)

Understanding what 4.3 changed is the right starting point for reasoning about 4.4. VAST 4.3 (December 2022) made three major changes:

  • SIMID formalized — SIMID 1.0–1.2 became the official mechanism for interactive creatives, replacing VPAID. The <InteractiveCreativeFile apiFramework="SIMID"> element is the recommended path for interactive linear ads. VPAID was fully retired.
  • Improved CTV measurement — Better support for impression reconciliation and viewability tracking in streaming and server-side insertion environments.
  • VPAID fully removed — After deprecation in 4.0 and discouragement in 4.1 and 4.2, VPAID is entirely absent from the 4.3 schema. Any tag using apiFramework="VPAID" is invalid in a VAST 4.3 document.

See the SIMID explained and VPAID explained pages for the full migration picture.

The VAST CTV Addendum 2024: a preview of VAST 4.4

Rather than wait for a new spec version, the IAB Tech Lab Advanced TV Working Group shipped the CTV Addendum 2024 as a set of <Extension>-based additions that work with VAST 2.0 and above. These extensions are the most likely candidates for native incorporation in a future 4.4 release.

ACIF: ad creative ID registration

The Ad Creative ID Framework (ACIF) defines a persistent identifier for ad creative that travels the video supply chain — similar to a UPC code for ads. The CTV Addendum added ACIF support via extension; VAST 4.4 is expected to give it a first-class element, likely as an extension of <UniversalAdId> or a new sibling element with a standardized registry attribute pointing to the ACIF authority.

Why it matters: ACIF enables reconciliation of impressions across DSP, SSP, and measurement vendor without relying on creative metadata that varies per partner. Ad servers and SSPs that implement ACIF early will have an advantage as more buyers require registered IDs.

DSA compliance icons

The EU Digital Services Act (Article 26) requires that ads displayed to users contain visible information identifying them as ads and disclosing the advertiser. The CTV Addendum added icon support across all VAST versions for DSA disclosure. VAST 4.4 is expected to standardize DSA-specific icon types natively alongside the existing Ad Choices icon pattern.

Why it matters: Any CTV or streaming publisher with EU inventory will need DSA-compliant tags. Tags that do not include a DSA icon where required will fail compliance checks. vastlint plans to add DSA icon validation rules once the schema is published.

Higher-resolution creative support

As large-format CTV displays (4K, 8K) become the norm, the <MediaFile> element's width and height constraints and the guidance around <Mezzanine> files need to reflect modern resolution requirements. The CTV Addendum included guidance here; 4.4 is expected to update the MediaFile schema accordingly.

Expected changes from open IAB issues

The IAB Tech Lab VAST GitHub repository has 14 open issues as of April 2026. Several have been open since before 4.3 shipped and are likely to be addressed in 4.4:

  • Missing notUsed tracking event (issue #44) — VAST 4.2 defines a notUsed event in spec prose but it is absent from the XSD. 4.4 is expected to add it formally.
  • Macro: continuous play context (issue #31) — A proposal to add a macro signaling whether an ad is playing in a continuous autoplay context (e.g., a streaming playlist) vs. a single play. Relevant for CTV mid-roll ad pods.
  • Codec reference update (issue #26) — The MediaFile codec guidance in VAST 4.x references older codec spec documents. 4.4 is expected to point to current H.264/HEVC/AV1 references, which matter for CTV creative quality validation.
  • XSD alignment with VAST 4.3 spec prose (issue #50) — The published XSD in the GitHub repository has not been updated for 4.3. A 4.4 release would ship with a fully aligned schema.

Agentic advertising: a likely VAST 4.4 influence

The IAB Tech Lab 2026 roadmap places agentic advertising at the center of its work. The ARTF (Agentic Real Time Framework) and AAMP 2.0 define how AI buyer and seller agents negotiate and execute programmatic deals. As agents begin trafficking VAST creative directly, the spec will need machine-readable fields for:

  • Creative approval status and provenance (links to ACIF)
  • Structured metadata for automated quality checks without parsing spec prose
  • Standardized error payloads that agents can interpret without natural language descriptions

Whether this surfaces in VAST 4.4 proper or in a separate ARTF/AAMP-VAST binding document is not yet clear. The vastlint MCP server already exposes VAST validation to AI agents via validate_vast and validate_vast_url today — see the agentic ad delivery guide for integration patterns.

What does not change in VAST 4.4

The core VAST structure has been stable since 4.0. These elements are expected to carry forward unchanged:

  • <InLine> / <Wrapper> chain structure
  • <Impression>, <Tracking>, <ClickThrough>
  • <MediaFile> with delivery, type, width, height
  • <UniversalAdId>, <AdVerifications> (OMID)
  • Wrapper depth semantics (5-hop default, per IAB recommendation)

SIMID will remain the interactive ad standard. There is no indication that SIMID is being revised in connection with a VAST 4.4 release.

How to prepare now

  1. Implement the VAST CTV Addendum 2024 extensions — these are already final and will be the baseline for 4.4. If your ad server or player supports them, migration to 4.4 will be minimal.
  2. Register creatives with ACIF — ACIF is live; registering IDs now means your tags will be 4.4-compatible as soon as the spec ships.
  3. Validate your 4.3 tags today — fixing existing spec violations in 4.3 will reduce the work needed when upgrading to 4.4. Use the web validator or the vastlint check CLI.
  4. Audit VPAID usage — VPAID was removed in 4.3 and will not return. Any pipeline still relying on VPAID creatives needs a migration path to SIMID before 4.4 adoption becomes a requirement.

When will vastlint support VAST 4.4?

vastlint will add VAST 4.4 validation rules as soon as the spec is published by IAB Tech Lab. The Rust core vastlint-core is structured so that new version rules can be added without breaking existing rule IDs — all 4.4 rules will have stable, new IDs distinct from the 2.0–4.3 set. Subscribe to the GitHub releases to be notified when 4.4 support ships.

Further reading