IAB Technical Standards: The Complete Reference

The programmatic advertising ecosystem runs on a foundation of technical standards maintained by the IAB Tech Lab. These specifications define how buyers and sellers communicate, how ads are delivered and measured, how user consent is transmitted, and how the supply chain is verified. For anyone working in ad tech—whether as a DSP engineer, SSP product manager, publisher operations lead, or advertiser—understanding the full landscape of IAB standards is essential. This reference covers every major specification, how they interconnect, and their current adoption status.

IAB Tech Lab Governance

The IAB Tech Lab is the technical standards body for the digital advertising industry, operating as a separate entity from IAB (Interactive Advertising Bureau). It maintains a working group structure where member companies—publishers, ad tech vendors, advertisers, and agencies—collaborate to develop and maintain specifications.

Standards Development Process

1. Proposal: A working group or member proposes a new specification or revision.
2. Development: The working group drafts the specification through iterative review cycles.
3. Public Comment: A draft is published for public comment (typically 30-60 days).
4. Finalization: Comments are addressed, and the specification is finalized and published.
5. Adoption: The industry implements the specification. The IAB Tech Lab provides conformance testing and certification programs.

The Standards at a Glance

OpenRTB: The Transaction Backbone

OpenRTB (Open Real-Time Bidding) is the foundational protocol for programmatic advertising. It defines the JSON message format for bid requests (sent by SSPs/exchanges to DSPs) and bid responses (sent by DSPs back to the exchange). First published in 2010, it has evolved through multiple versions to support display, video, native, audio, and DOOH (Digital Out-of-Home) ad formats.

Key Components

• Bid Request: Contains information about the impression (ad format, size, position), the user (demographics, consent), the publisher (site/app details), and the device (OS, screen, connection).
• Bid Response: Contains the bid price, creative ID, ad markup (HTML, VAST tag, or native assets), and targeting information.
• Win Notification: Sent by the exchange to the winning DSP after the auction concludes, enabling post-bid tracking.

OpenRTB 2.5 vs. 2.6

OpenRTB 2.5 (2016) remains widely deployed, but 2.6 (2022) introduced significant improvements including native support for privacy regulations (GDPR, CCPA), structured supply chain data, enhanced audio and video support, and improved DOOH transaction objects. The transition to 2.6 has been gradual, with many platforms supporting both versions simultaneously.

AdCOM: The Data Model Layer

AdCOM (Advertising Common Object Model) is a specification that defines shared data structures used across multiple IAB standards. Rather than redefining objects like Device, User, Site, and App in each protocol, AdCOM provides canonical definitions that OpenRTB, other transaction protocols, and measurement systems can reference.

AdCOM reduces redundancy and ensures consistency across the standards ecosystem. When OpenRTB 2.6 references a Device object, it uses the AdCOM definition, ensuring that a device identified in a bid request has the same structure as a device reported in a measurement event.

VAST: Video Ad Delivery

VAST (Video Ad Serving Template) defines the XML format for delivering video ad creatives from ad servers to video players. It supports linear (pre-roll, mid-roll, post-roll), non-linear (overlay), and companion ad formats. VAST tags contain media file URLs, tracking pixel endpoints, and interactive element definitions.

VAST 4.2 (the current version) added native support for SIMID, improved CTV compatibility, enhanced closed caption handling, and mezzanine file support for server-side ad insertion (SSAI) workflows. It also improved integration with the OM SDK for standardized viewability measurement.

SIMID: Secure Interactive Video

SIMID (Secure Interactive Media Interface Definition) is the modern replacement for VPAID. It provides a standardized, secure communication protocol between video players and interactive ad creatives using a message-based architecture. Unlike VPAID, which gave ads full access to the publisher's page context, SIMID sandboxes the ad in an iframe and uses postMessage for controlled, bidirectional communication.

SIMID was designed to address VPAID's security vulnerabilities, performance issues, and tight coupling between ads and players. It supports the same interactive capabilities (click-through, expand, fullscreen, navigation) while providing better isolation and error handling.

MRAID: Mobile Rich Media

MRAID (Mobile Rich Media Ad Interface Definitions) enables interactive rich media ads to function within mobile app environments. It defines a JavaScript API that ad creatives can call to interact with the host app's SDK—requesting expand, resize, fullscreen, close, and other actions. MRAID also provides standardized viewability signals to ad creatives.

MRAID 3.0 (2018) added support for native-style ads, improved viewability measurement, and better handling of audio state and orientation changes. It remains the primary standard for in-app rich media advertising across iOS and Android.

Native Ads Specification

The IAB Native Ads specification defines how native advertising content is structured and delivered programmatically. It provides two approaches:

• Content Template: A structured JSON format defining native ad components (title, description, image, CTA, etc.) that publishers can render to match their site design.
• Pre-rendered Markup: HTML or other markup that the ad server has pre-rendered, which the publisher embeds with minimal modification.

The native specification integrates with OpenRTB through the native bid request/response objects, enabling programmatic trading of native ad inventory alongside display and video.

Trust & Safety Standards

ads.txt and app-ads.txt

These publisher authorization standards declare which advertising systems are authorized to sell a publisher's inventory. ads.txt is hosted on web domains, while app-ads.txt is discovered through app store listings. Both use the same four-field record format (domain, account ID, relationship type, certification authority ID). They are essential for combating domain spoofing and unauthorized reselling.

sellers.json

Hosted by SSPs and exchanges, sellers.json discloses the identity of each publisher whose inventory they sell. It maps seller IDs (matching ads.txt account IDs) to entity names and domains, enabling buyers to verify that the seller in a bid request actually represents the claimed publisher.

SupplyChain Object (schain)

The schain object is embedded in OpenRTB bid requests to document the complete path of entities through which the request has passed. Each entity appends a node with its identifier, enabling buyers to perform supply path optimization, detect unauthorized intermediaries, and verify the authenticity of the supply chain.

Privacy: TCF 2.2

The Transparency & Consent Framework enables standardized collection and transmission of user consent across the programmatic supply chain. TCF 2.2, the current version, supports consent and legitimate interest as legal bases under GDPR, requires data retention disclosure from vendors, and mandates enhanced user transparency in CMP interfaces. The TC String is transmitted through OpenRTB bid requests, enabling all supply chain participants to act on the same consent data.

Measurement: OM SDK

The Open Measurement SDK provides a standardized integration point for viewability and verification measurement across mobile apps, web, and CTV. Publishers integrate the OM SDK once, and all participating verification vendors can measure through it. The SDK tracks ad sessions, geometry data, obstruction information, and playback events, passing this data to verification scripts for viewability calculation.

How the Standards Interconnect

The IAB standards are not isolated specifications—they form an interconnected system where each standard references and supports others:

Transaction Flow

1. A publisher integrates OM SDK for measurement and hosts ads.txt for authorization.
2. The publisher's SSP sends a bid request via OpenRTB, including schain nodes, TCF consent strings, and OM SDK availability signals.
3. The DSP evaluates the bid request, verifying ads.txt authorization, parsing TCF consent, and analyzing the schain path.
4. The DSP responds with a bid containing a VAST tag (for video) or native assets (for native).
5. The VAST tag may include SIMID interactive elements and OM SDK verification scripts.
6. The SSP's sellers.json confirms the publisher's identity to the buyer.

A single programmatic impression typically touches six or more IAB standards: OpenRTB for the transaction, ads.txt and schain for trust verification, TCF for consent, VAST or Native for creative delivery, and OM SDK for measurement. Understanding how these standards interconnect is critical for building robust ad tech systems.

Adoption Status and Industry Trends

Emerging Standards and Future Directions

The IAB Tech Lab continues to develop new specifications and evolve existing ones to address emerging challenges:

• OpenRTB 3.0: A major restructure that separates the protocol layer from the object model (AdCOM), improving extensibility and reducing implementation complexity.
• Seller Defined Audiences (SDA): Enables publishers to share first-party audience segments in bid requests while respecting privacy regulations.
• Ad Manager API: Standardized APIs for ad operations, enabling automation of campaign management, trafficking, and reporting across platforms.
• DOOH Standards: Extended OpenRTB support for digital out-of-home advertising, including location data, venue types, and measurement frameworks specific to physical-world ad placements.
• Privacy-First Standards: Ongoing work to support post-cookie advertising, including integration with Google's Privacy Sandbox, UID2, and other identity solutions.

Resources for Implementation

The IAB Tech Lab provides extensive resources for developers implementing these standards:

• Full specification documents available at iabtechlab.com
• Reference implementations and sample code for OpenRTB, VAST, and OM SDK
• Conformance testing tools for validating implementations
• Working group participation for companies that want to influence future specifications
• Certification programs for CMPs, SSPs, and DSPs demonstrating standards compliance