Media Rating Council issues draft standards for digital ad auction transparency

The Media Rating Council released a draft document in September 2025 outlining comprehensive transparency requirements for digital advertising auctions across multiple channels, including display, text, video, audio, search, social, retail media, streaming connected TV, and addressable television. According to the MRC, the draft represents its effort to establish standards for transparency, disclosure, and reporting of various aspects and results of digital advertising auctions.

The standards emerged from a collaborative project initiated by Omnicom, with backing from the American Association of Advertising Agencies (4A's), the Association of National Advertisers (ANA), World Federation of Advertisers (WFA), and the Interactive Advertising Bureau (IAB) Tech Lab. Comments on the draft will be accepted through October 20, 2025, via email to the MRC.

Addressing industry-wide transparency gaps

No standards currently exist for ad auctioneer conduct regarding disclosure and reporting of auction rules or transparency into auction processes and outcomes. The document states that the objective of these standards is to promote transparency around auction rules and scoring along with reporting and standardization where possible and appropriate, to ensure that auction rules and outcomes are understood for all parties.

Hundreds of billions of ad impressions are auctioned, sold, and delivered worldwide every day. The vast majority of auction-based media spend is now transacted through "closed-loop" auctions, where all functions are hosted entirely by platform ad auctioneers across channels like search, social, and retail media. Each platform maintains proprietary auction systems, and users of these systems may have limited information regarding how these auctions operate.

A smaller but significant portion of ad auctions occurs in the "programmatic" ecosystem, characterized by utilization of the OpenRTB standard. The standards are not aimed at any one platform, ad auctioneer, or auction type. The intent is not to replace or alter existing industry protocols such as OpenRTB but to supplement them with guidance regarding methods, disclosures, and outcome reporting.

Technical requirements and auction mechanics

The draft establishes requirements for organizational structure and auction administration that apply to all ad auctioneers. At minimum, formalized responsibility for auction integrity within the auctioneer organization should exist, including a designated contact for auction participants. The standards encourage establishment of dedicated teams or specific personnel responsible for supporting and overseeing the auction process, including adherence to policies, performance, changes, and communications.

For closed-loop ad auctioneers, the standards mandate disclosure of auction types, including whether systems employ first-price, second-price, or modified second-price mechanisms. The exact method by which winning bids are converted to final clearing prices should be directly reported. Variables that affect nominal to effective bid conversion must be made known in general and reported to auction participants where applied.

How discounts and technology fees are applied should be consistent and transparent. The standards state that fees are encouraged to be applied pre-auction ("net bidding") to encourage efficient competition within the ecosystem, while discounts should be applied post-auction. The method for determining ad relevance scores should be disclosed and specific scores reported. Critically, the interaction between relevance scores and bid conversion must be made clear.

Reserve prices must be clearly disclosed to auction participants. At minimum, the reserve price should be directly reported before an auction is run and after it concludes. Reserve prices should not be set on a per-buyer basis—the same floor should apply simultaneously to all buyers.

Variables and the relative weighting of said variables that affect winner determination should be made known and reported where applied to enable buyers and sellers to understand win/loss reasons. The method for constructing variables such as ad relevance scores, quality, context, and priority rules should be disclosed and the actual applied variables reported.

OpenRTB and programmatic requirements

For ad auctioneers operating in open programmatic and utilizing OpenRTB, the standards strongly encourage use of several key attributes within the Open RTB Protocol. Transaction ID (tid) helps link bids from different bidders to specific ad impressions, facilitating attribution and reporting. While complete usage of the Source object is strongly encouraged, using the Transaction ID as specified in the OpenRTB spec in a bid request is the minimum requirement contingent on DSP adoption of Multi-Bid.

The Global Placement ID (gpid) provides a unique identifier for an ad placement, ensuring consistent recognition across different platforms, buyers, and sellers. By providing this single, standardized reference point, the GPID enhances transparency, allowing buyers to know exactly where their ads will appear.

Both the SupplyChain object and SupplyChainNode object (including the RequestId) should be used to its fullest extent and be complete. Buying platforms should provide reporting against both the Transaction ID and RequestID object to all buyers. Multi-bid, where a DSP sends multiple bids for the same ad impression in a single RTB auction, is strongly encouraged whenever possible.

For all connected TV inventory, podded bidding, made available in OpenRTB 2.6, is deemed the best practice for merchandising all CTV supply programmatically. Buyers are encouraged to use multi-bid when appropriate, particularly in concert with podded bidding bid requests. Appropriate Loss Codes should be passed from seller to buyer for all transactions and appropriately reported by the buy-side platform.

Reporting and measurement requirements

All auction operators should provide data-based reporting that enables auction participants to understand what they paid and how that price was determined, in detail. Results of auctions should be reported in a syndicated or machine-readable format for auction participants. This includes bid factors applied such as likelihood to purchase or convert and quality scores. Line-item granularity is encouraged, as is reporting latency availability of all auction results on a next day or 24-48 hour basis.

Sampling is allowed to facilitate reporting, but sampling rules should be generally disclosed by ad auctioneers to auction participants and designed to be representative of typical ad auction activity. Sampling will be subject to the MRC's sampling operational and disclosure requirements in the MRC Minimum Standards where applicable as part of MRC audits.

Ad delivery and activity measurement provided by ad auctioneers or third-party measurement vendors inclusive of impressions, clicks, viewability, invalid traffic, audience, brand safety, and other metrics should adhere to IAB and MRC Guidelines and Standards for measurement where applicable and are encouraged to be subject to independent validation through MRC accreditation audit. Bid information discussed throughout the standard is strongly encouraged to be made available to third-party measurement providers where possible to enable independent measurement and reporting.

The standards encourage third-party measurement where possible, including accredited invalid traffic and content level brand safety measurement on a pre and post basis, as well as compliance with industry transparency efforts such as ads.txt and app.txt, authorized resellers, referrers, and traffic sourcing declarations. Pre-bid qualification, including evaluation of bid requests based on quality, invalid traffic, or buyer-defined parameters, is encouraged.

Disclosure and change management

All ad auctioneers should provide detailed disclosure to users related to auction methods applied, including models and adjustment, as supported by documentation and empirical support. In addition to requirements throughout the standards related to specific disclosures of methods, variables, terms, and rules applied in ad auctions, ad auctioneers should supply auction participants with user guides, explainers, and help guides detailing auction dynamics and functionality.

Changes to auction systems or methods should be proactively communicated to auction participants in advance. These disclosures may take the form of formal release notes or other means, but at minimum, a formal change notification policy compliant with MRC Minimum Standards should be developed and adhered to. Ad auctioneers should also maintain version histories of auction systems or methods made available to auction participants and provide impact assessments to end users for meaningful changes.

Errors or variability associated with estimates, models, or other bid factors and variables involved in the auction should be disclosed. MRC Minimum Standards require disclosure and quantification of sampling and non-sampling error and variability, and these requirements apply to ad auctioneers seeking to be compliant with the standards.

Auditing and certification framework

Third-party independent auditing is encouraged for all auction systems and operators, particularly those not utilizing industry standard communication protocols such as OpenRTB (closed-loop auctions). Ad auctioneers are encouraged to voluntarily submit for MRC accreditation audit against the standards as well as to utilize measurement and report of ad delivery that is audited and accredited.

Auction operators and systems are recommended to be certified as compliant with the standards at minimum annually by voluntarily submitting to independent audit. This recommendation is strongly supported by the 4As, ANA, WFA, and other members of the buying community. In addition to MRC, there are a number of other certifiers and types and levels of certification available to organizations involved in media measurement and ad auctioneers.

The MRC encourages non-U.S. measurers of activity to adopt the practices spelled out in the standards. While certification regimes may vary on a country-by-country basis, the organization encourages measurers and ad auctioneers to be audited for compliance annually by independent, third-party auditing organizations.

Context within the broader transparency movement

The development of these standards occurs amid intensifying scrutiny of digital advertising auction practices. US District Judge Amit Mehta delivered a comprehensive 230-page ruling on September 2, 2025, requiring Google to publicly disclose material changes it makes to its ad auctions. The ruling addressed the court's finding that for years Google's ad auction adjustments led to higher text ad prices that escaped advertiser notice.

Federal regulators have also taken action, with the FTC investigating both Amazon and Google over search ad pricing disclosures in September 2025. The investigations centered on transparency in advertising auction practices, including whether companies disclosed reserve pricing for search advertisements and whether they increased advertising costs without proper disclosure to advertisers.

Legislative efforts have emerged as well. Senator Mike Lee reintroduced the AMERICA Act on March 13, 2025, which includes transparency requirements mandating that brokerages provide customers with information to verify compliance with their obligations, including data on bids, pricing, and routing practices upon request.

The programmatic advertising ecosystem has experienced significant infrastructure disputes in 2025. Prebid.org implemented bidder-specific transaction identifiers on August 27, 2025, eliminating cross-exchange visibility that the OpenRTB specification originally intended to provide. The IAB Technology Laboratory issued a statement declaring the implementation "materially violates the OpenRTB specification."

In response to these transaction ID changes, The Trade Desk announced OpenAds on October 2, 2025, a platform designed to maintain transparency. CEO Jeff Green described it as necessary to preserve fair auction mechanics after Prebid.org disabled cross-exchange transaction ID functionality. The company open sourced the underlying OpenAds auction code, allowing industry participants to inspect auction mechanics directly.

Implications for the marketing community

The standards framework addresses fundamental operational challenges that have plagued programmatic advertising. Industry data shows 72% of marketers plan to increase programmatic advertising investment in 2025, marking significant growth from 62% in 2024. However, transparency concerns persist despite this expansion.

Without clear auction rules and transparency, advertisers face significant risks. If advertisers believe they are bidding into one sort of auction but are in fact bidding into another sort altogether, the auction stops working efficiently. Bid strategies that are ideal for a first-price auction become suboptimal for a second-price auction. This lack of information presents risks for efficient market operation.

The standards do not stipulate or standardize the design of any auction type, as auctioneer companies can and should design auction systems to best suit the particular characteristics of a given media form. Rather, the standards seek to stipulate requirements and guidance to ensure that auctioneers clearly explain to advertisers how their auctions determine pricing and allocation, and provide accountability via reporting so that users can validate the same.

Measurement standardization remains a significant challenge across digital advertising channels. Traditional campaigns often operate with disparate measurement methodologies, making cross-platform performance comparison difficult for advertisers. The MRC standards aim to provide consistent frameworks for auction transparency and reporting that could extend across multiple channels.

The development of these standards originated from research efforts undertaken by the MRC and the Standards Steer Team to delineate various auction models and rules currently employed across the industry. These research efforts assessed current disclosures and reporting related to auctions to provide a more complete view of the current state of auction systems, highlight common practices, explore key differences, and identify specific best practices.

Several major ad auctioneers provided confidential details and data to the Steer Team for review and aggregated summary to the broader working group. The type of information gathered included types of auction systems used, how winners of auctions are determined, how prices that winners must pay are set, use of reserve prices and methods to update them over time, use of advance information about bids and budgets to adjust auction functioning, how often rules of auction systems are updated and disclosed to users, and what information is presently disclosed or reported about auction systems and outcomes.

The standards were developed with participation of a large tripartite group of media content providers, advertising agencies, advertisers, vendors and consultants, ad auctioneers, measurement organizations, and other interested organizations. They involved participation of major buyer-side trade organizations and their constituents and were thereafter provided to the public through a formal period of public comment prior to adoption.

At minimum, the standards are available for auction participants to set expectations regarding reporting, disclosure, and transparency and for ad auctioneers to strive to adhere to them. While third-party auditing and MRC accreditation auditing is voluntary, supporting and sponsoring industry organizations may encourage compliance with the standards as well as independent audit verification as part of separate efforts at their discretion.

Timeline

• September 2025 – Media Rating Council releases draft Digital Advertising Auction Transparency Standards for public comment, establishing first industry-wide framework for auction disclosure requirements
• October 20, 2025 – Deadline for public comments on MRC draft standards
• October 2, 2025 – The Trade Desk announces OpenAds platform with open-source auction code to maintain transparency after transaction ID changes
• September 14, 2025 – FTC investigates Amazon and Google over search ad pricing disclosures and reserve pricing transparency
• September 2, 2025 – US District Judge requires Google to publicly disclose material ad auction changes in 230-page antitrust ruling
• August 30, 2025 – Prebid breaks transaction ID tracking system, removing transparency tools for detecting auction manipulation
• August 27, 2025 – Prebid.org implements bidder-specific transaction identifiers, IAB Tech Lab declares it materially violates OpenRTB specification
• March 13, 2025 – Senator Mike Lee reintroduces AMERICA Act with transparency requirements for ad brokerages including bid, pricing, and routing data
• 2023 – IAB Tech Lab develops comprehensive curation framework establishing technical standards for programmatic advertising
• 2018 – AppNexus reworks publisher contracts to enable fee transparency

Summary

Who: The Media Rating Council, a non-profit industry self-regulatory body established in 1963, released the standards in collaboration with Omnicom, the American Association of Advertising Agencies (4A's), the Association of National Advertisers (ANA), World Federation of Advertisers (WFA), and the Interactive Advertising Bureau (IAB) Tech Lab. The standards affect ad auctioneers, advertisers, agencies, measurement providers, and publishers across the digital advertising ecosystem.

What: A comprehensive draft document outlining requirements, guidance, and best practices for transparency, disclosure, and reporting of digital advertising auctions. The standards address auction types (first-price, second-price, modified second-price), bid conversion processes, reserve pricing, winner determination, reporting requirements, change disclosure protocols, and independent auditing guidelines. The framework covers display, text, video, audio, search, social, retail media, streaming connected TV, and addressable television channels.

When: The MRC released the draft standards in September 2025, with a public comment period extending through October 20, 2025. Comments can be submitted via email to rpinelli@mediaratingcouncil.org. The final standard will be published following the comment period and will be reassessed periodically to ensure continued applicability.

Where: The standards apply globally to all digital advertising auctions, including closed-loop platform auctions (search, social, retail media) and open programmatic ecosystems utilizing OpenRTB. While developed with significant input from U.S. industry organizations, the MRC encourages international adoption with audit compliance by independent third-party auditing organizations adapted to country-specific certification regimes.

Why: No standards previously existed for ad auctioneer conduct regarding disclosure and reporting of auction rules or transparency into auction processes and outcomes. Hundreds of billions of ad impressions are auctioned daily with users having limited information about how proprietary systems operate. Without clear auction rules, advertisers cannot develop optimal bid strategies, potentially paying higher prices or receiving less favorable outcomes. The standards aim to ensure both buyers and sellers understand how auction rules work, how winning bids are chosen, and how final prices are calculated, enabling fair and efficient market operation while supporting independent auditing and verification.