IAB Tech Lab challenges Prebid transaction ID changes

The IAB Expertise Laboratory issued a strong statement declaring that current changes in Prebid’s implementation of the Transaction ID (tid) field materially violate the OpenRTB specification. In line with Anthony Katsur, Chief Govt Officer at IAB Tech Lab, “The Tech Lab doesn’t endorse this method, because it dangers undermining the integrity and consistency of open technical requirements which are essential to interoperability throughout the programmatic ecosystem.”

The assertion, revealed on August 27, 2025, represents a big escalation in tensions between the requirements physique and the header bidding wrapper. It marks the primary time the IAB Tech Lab has instantly contradicted a significant implementation choice by Prebid.org, elevating questions on the way forward for technical requirements coordination in programmatic promoting.

Technical requirements at stake

The controversy facilities on transaction identifiers, which function distinctive public sale identifiers throughout all suppliers all through the whole provide chain. These identifiers doc distinctive impression transactions and allow demand-side platforms to deduplicate auctions and optimize bidding methods.

In line with the OpenRTB specification, transaction IDs should be frequent throughout all members in bid requests. The usual requires that “transaction ID should be frequent throughout all members on this bid request (e.g., probably a number of exchanges).”

Nonetheless, Prebid lately modified its implementation to generate distinctive transaction IDs for every bidder reasonably than sustaining a constant identifier throughout all exchanges. This alteration eliminates the first deduplication mechanism that demand-side platforms relied upon to establish duplicate public sale alternatives.

The modification impacts how patrons establish when a number of bid requests characterize the identical impression alternative. Beforehand, DSPs may use transaction IDs to forestall bidding on duplicate auctions and implement provide path optimization methods.

Technical implementation particulars

The adjustments implement bidder-specific transaction identifiers in a number of key areas. The ortb2Imp.ext.tid area now generates distinctive values for every bidder and transaction ID pair. Equally, ortb2.supply.tid creates distinctive identifiers for every bidder. Each modifications ignore first-party knowledge that publishers could have configured.

GitHub documentation reveals that the auctionId and transactionId properties of bid requests now reference ortb2.supply.tid and ortb2Imp.ext.tid respectively. This represents a basic shift in how Prebid handles public sale identification throughout the availability chain.

The implementation adjustments make sure that every bidder receives totally different transaction identifiers, even when collaborating in an identical public sale alternatives. This modification eliminates the cross-exchange visibility that the OpenRTB specification meant to supply.

Publishers utilizing Prebid Server integration face explicit challenges. In line with technical documentation, the identical logic should be carried out server-side since there exists just one location for supply.tid and ext.tid in Prebid Server requests.

Business response patterns

The modification has generated important dialogue throughout programmatic promoting channels. Commerce publication AdTechRadar reported that the change “probably removes a broadly adopted mechanism for provide deduplication,” noting issues about duplicate bids, wasted spend, and better prices.

Ari Paparo, CEO of Marketecture, described the event as “breaking information” on social media, explaining that “Prebid.org pushed out a breaking change to Prebid.js that makes the distinctive ID of each public sale (TID) not work throughout exchanges.”

Publishers expressed combined reactions to the implementation adjustments. Some acknowledged issues about yield compression that might consequence from patrons utilizing transaction IDs to establish cheaper provide paths. Others questioned the privateness rationale, arguing that established knowledge safety mechanisms already deal with identifier linking issues.

A number of business members famous the timing significance. The adjustments happen amid ongoing discussions about provide path optimization and transparency initiatives throughout programmatic promoting platforms.

Privateness issues driving change

In line with discussions within the Prebid neighborhood, privateness issues motivated the implementation modifications. Publishers expressed issues that unified transaction IDs may allow patrons to sew bid requests collectively throughout totally different sellers, probably exposing connections between identifiers that publishers most well-liked to maintain separate.

The privateness rationale facilities on stopping patrons from utilizing transaction IDs as linking keys throughout bid requests and exchanges. This might theoretically permit demand-side platforms to detect relationships between writer stock sources or person identifiers that weren’t meant to be linkable.

Business members famous that Prebid authorized counsel and the writer committee modified the default setting for transaction identifiers to false two years in the past. This earlier change was designed to guard writer contractual obligations and person privateness whereas permitting publishers to allow the performance at their discretion.

Nonetheless, the current modifications transcend default settings. They basically alter how transaction IDs perform, no matter writer preferences or configuration selections.

IAB Tech Lab’s collaborative method

The requirements physique emphasised its dedication to discovering business options reasonably than unilateral implementations. In line with Katsur, “The proper path ahead is to not bypass or reinterpret the specification, however to work collaboratively on it.”

The IAB Tech Lab introduced plans to convene a devoted discussion board with publishers, patrons, and expertise companions. The group goals to “chart a path ahead that addresses the underlying business issues whereas sustaining compliance with OpenRTB.”

The collaborative method acknowledges the strain that transaction IDs have created inside the writer neighborhood. In line with the assertion, “We totally acknowledge the strain that the tid area has induced inside the writer neighborhood. Nonetheless, making unilateral adjustments exterior the bounds of the specification creates fragmentation and uncertainty for patrons, sellers, and intermediaries alike.”

This represents a big shift in how technical requirements are developed and carried out. Fairly than permitting particular person organizations to interpret specs independently, the IAB Tech Lab advocates for coordinated business discussions earlier than implementation adjustments.

Historic context and precedent

The OpenRTB specification has undergone quite a few updates since its preliminary launch. Earlier modifications usually adopted formal remark intervals and business session processes. Main adjustments required intensive dialogue amongst working group members earlier than finalization.

IAB Tech Lab has previously clarified video placement definitions and up to date specs to assist new promoting codecs. These modifications adopted established procedures for technical customary evolution.

The group has additionally launched specs for rising applied sciences, together with updates to support Google’s Protected Audience API and new protocols for first-party data matching.

The Prebid transaction ID controversy represents the primary main occasion the place the requirements physique publicly challenged an implementation that diverged from established specs.

Market implications and technical debt

The adjustments create quick challenges for demand-side platforms that constructed optimization methods round constant transaction identifiers. These platforms should now reassess their deduplication logic and provide path optimization mechanisms.

Publishers face uncertainty about purchaser necessities and expectations. Many carried out transaction ID assist particularly as a result of demand companions requested the performance for transparency and deduplication functions.

Provide-side platforms should consider their very own implementations to make sure compatibility with each the OpenRTB specification and the modified Prebid conduct. This creates potential fragmentation in how totally different expertise platforms deal with transaction identification.

The technical modifications additionally have an effect on measurement and attribution programs that relied on constant transaction identifiers for cross-platform monitoring and evaluation. These programs should adapt to the brand new bidder-specific identifier mannequin.

Ahead-looking technical issues

The IAB Tech Lab’s name for collaborative resolution growth suggests potential specification updates to deal with the underlying issues. These modifications may formalize privateness protections whereas sustaining cross-exchange transaction visibility.

Potential options may embody non-compulsory transaction ID scoping, publisher-controlled identifier insurance policies, or enhanced privateness controls inside the present framework. The devoted discussion board introduced by the IAB Tech Lab will probably discover these technical alternate options.

The controversy highlights broader challenges in balancing transparency, privateness, and technical requirements in programmatic promoting. Because the business evolves, coordination between requirements our bodies and implementation organizations turns into more and more essential.

Timeline

Abstract

Who: IAB Expertise Laboratory, led by CEO Anthony Katsur, formally challenged Prebid.org’s implementation of transaction ID modifications that have an effect on programmatic promoting requirements compliance.

What: The IAB Tech Lab declared that Prebid’s current adjustments to transaction ID implementation materially violate the OpenRTB specification by creating bidder-specific identifiers as a substitute of sustaining constant transaction IDs throughout all public sale members.

When: The assertion was revealed on August 27, 2025, following Prebid’s implementation of bidder-specific transaction ID adjustments of their newest model replace.

The place: The announcement impacts the worldwide programmatic promoting ecosystem, impacting publishers, demand-side platforms, supply-side platforms, and intermediaries that depend on OpenRTB requirements for interoperability.

Why: The battle arose from Prebid’s try to deal with writer privateness issues about transaction IDs probably enabling purchaser knowledge stitching throughout exchanges, whereas the IAB Tech Lab maintains that unilateral specification adjustments undermine technical requirements and business interoperability.

PPC Land explains

Transaction ID (TID): A singular identifier assigned to every public sale alternative that permits all members within the programmatic provide chain to acknowledge when a number of bid requests characterize the identical impression. The OpenRTB specification requires these identifiers to stay constant throughout all exchanges and suppliers for a single public sale, permitting demand-side platforms to implement deduplication methods and provide path optimization.

OpenRTB: The Actual-Time Bidding protocol developed by the IAB Expertise Laboratory that standardizes communication between patrons and sellers in programmatic promoting auctions. This specification defines technical necessities for bid requests, responses, and associated knowledge buildings that allow interoperability throughout totally different promoting expertise platforms.

IAB Tech Lab: The Interactive Promoting Bureau Expertise Laboratory, a non-profit consortium that develops foundational technical requirements for digital promoting. Established in 2014, the group maintains specs together with OpenRTB, advertisements.txt, and numerous privacy-enhancing protocols that facilitate programmatic promoting operations.

Prebid: An open-source header bidding wrapper that permits publishers to conduct unified auctions throughout a number of demand sources concurrently. Prebid.org operates as each the group managing this expertise and the neighborhood of builders, publishers, and promoting expertise corporations that contribute to its growth.

Provide Path Optimization (SPO): The apply by which demand-side platforms analyze and optimize the routes by way of which they buy promoting stock. This course of depends on constant transaction identifiers and different bidstream alerts to establish duplicate alternatives, consider middleman charges, and direct spending towards probably the most environment friendly provide sources.

Demand-Aspect Platform (DSP): Expertise platforms that allow advertisers and businesses to buy digital promoting stock programmatically throughout a number of publishers and advert exchanges. These platforms use transaction IDs and different bidstream knowledge to optimize marketing campaign efficiency and forestall duplicate bidding on the identical impression alternatives.

Deduplication: The technical strategy of figuring out and eliminating duplicate bid requests that characterize the identical impression alternative however arrive by way of totally different provide paths. This mechanism prevents advertisers from competing towards themselves in auctions and reduces wasted promoting spend throughout the programmatic ecosystem.

Bidstream: The continual move of bid requests and responses that happens throughout real-time bidding auctions. This knowledge stream accommodates technical details about obtainable promoting stock, together with transaction identifiers, placement particulars, person info, and different alerts that allow programmatic shopping for selections.

Writer Privateness: The idea encompassing publishers’ issues about defending their stock sources, person knowledge, and enterprise relationships from extreme transparency that might allow unfavorable purchaser behaviors. Within the context of transaction IDs, these issues give attention to stopping patrons from utilizing constant identifiers to map writer relationships or optimize towards writer pursuits.

Technical Requirements Compliance: The adherence to established specs and protocols that guarantee interoperability between totally different promoting expertise programs. The IAB Tech Lab’s problem to Prebid facilities on sustaining specification integrity and stopping fragmentation that might undermine the programmatic promoting ecosystem’s technical foundations.