Prebid clarifies transaction ID policy after industry confusion

Prebid.org released a statement on October 23, 2025, addressing recent confusion around Transaction ID handling in Prebid.js. The clarification follows months of industry debate that began in August 2025 when the organization modified how Transaction IDs function within its header bidding wrapper.

According to the statement written by Garrett McGrath, Transaction IDs were originally added to the OpenRTB specification in 2013. Prebid.js version 8 introduced support for TIDs in June 2023. From the beginning, TIDs in Prebid have operated on an opt-in basis. Publishers who wish to send TIDs must enable them manually—a policy that continues today.

The opt-in approach stemmed from legal guidance and publisher feedback regarding data-sharing concerns. This decision reflected concerns within the publisher community about how Transaction IDs could potentially be used by demand-side platforms to map supply paths and optimize spending toward cheaper routes.

Earlier this year, TIDs became a point of contention across the programmatic ecosystem. Some DSPs began requiring them as a condition for spend. The pressure from demand-side platforms created challenges for publishers who had chosen not to enable TIDs, while simultaneously raising concerns among those who had about potential yield compression.

The IAB Tech Lab issued a statement on August 27, 2025, declaring that Prebid's implementation of bidder-specific Transaction IDs "materially violate the OpenRTB specification." Anthony Katsur, Chief Executive Officer at IAB Tech Lab, stated the organization does not endorse the approach because it risks undermining the integrity and consistency of open technical standards critical to interoperability across the programmatic ecosystem.

The August 2025 decision to modify TID handling came from the Prebid Publisher Committee, not a small group of resellers as some industry discussions suggested. The committee voted to make Transaction IDs SSP-specific rather than global. According to the statement, this decision reflected broad community consensus and aimed to promote flexibility across the market.

Prebid.js version 10.0 was released in July 2025. The new TID logic was implemented in version 10.9, which followed the major version release. Publishers typically take considerable time to adopt major version updates. As a result, the new SSP-specific TID logic currently accounts for approximately 1% of total Prebid traffic. The remaining 99% of TIDs continue using the original global format.

Publishers expressed concerns about yield compression that could result from buyers using Transaction IDs to identify and systematically choose lower-cost supply paths. Some questioned the privacy rationale, arguing that established data protection mechanisms already address identifier linking concerns. The timing proved significant amid ongoing discussions about supply path optimization and transparency initiatives.

The modification to SSP-specific identifiers eliminated the cross-exchange visibility that the OpenRTB specification originally intended to provide. Demand-side platforms lost their ability to detect when they received multiple bid requestsfor the same advertising opportunity across different supply-side platforms. This created the first major standards clash between the header bidding wrapper and the industry standards body.

According to the OpenRTB specification, Transaction IDs must remain common across all participants in bid requests. The standard explicitly requires that transaction IDs be consistent across exchanges for the same auction opportunity. Prebid's implementation of bidder-specific identifiers broke this fundamental requirement.

Michael Sullivan from The Trade Desk described the impact during a Marketecture Podcast recorded on August 28, 2025. He characterized it as a breaking change affecting major publishers including The New York Times, CNN, Forbes, Fox News, BBC, and Reuters. Sullivan argued that Transaction IDs served broader market health beyond individual advertiser benefits.

In response to the confusion and the small percentage of traffic affected, Prebid.org will release an additional update this week. The update will allow publishers using the latest version of Prebid.js who have opted to pass TIDs to choose whether to send global or SSP-specific Transaction IDs. All earlier versions of Prebid.js will remain unchanged and continue sending a single global TID when enabled.

This flexibility represents a significant shift from the August implementation. Publishers running version 10.9 or later who have opted into Transaction IDs will gain control over which format they transmit. Those on earlier versions will see no changes to their existing implementations.

The statement emphasized that 99% of Prebid traffic continues operating under the original global TID format due to the gradual adoption rates of major version updates. Publishers who have not upgraded to version 10.0 or later continue using the global Transaction ID system without any modifications.

The Trade Desk announced OpenAds on October 2, 2025, a platform designed to maintain transparency despite the Transaction ID changes. CEO Jeff Green stated the company branched Prebid's codebase to create what he described as "an upgraded auction" reflecting Prebid's mechanics prior to the Transaction ID modifications. The Trade Desk reported that Transaction ID coverage reached 59% of browser-based ads on the open internet before the changes.

Raptive proposed an alternative solution on September 18, 2025, suggesting encrypted Transaction IDs combined with bid transparency feeds and multi-bidding requirements. Chief Strategy Officer Paul Bannister outlined the three-component solution designed to balance publisher privacy concerns with advertiser transparency needs.

The programmatic advertising ecosystem has grappled with transparency challenges throughout 2025. The Transaction ID controversy highlights fundamental tensions between technical standardization and commercial interests in the supply chain. Publishers seek to protect yield while buyers demand tools to optimize spending and detect auction manipulation.

For publishers using Prebid Server integration, the situation presents particular technical challenges. Server-side implementation requires the same logic due to limited locations for source.tid and ext.tid in Prebid Server requests. Publishers invested engineering resources in Transaction ID support based on OpenRTB specifications now face decisions about whether continued support provides value under the modified system.

The IAB Tech Lab called for collaborative solutions rather than unilateral implementations. Katsur stated that the right path forward involves working collaboratively on specifications rather than bypassing or reinterpreting them. The organization announced plans to convene a forum with publishers, buyers, and technology partners to chart a path forward addressing industry concerns while maintaining OpenRTB compliance.

Brian O'Kelley, Co-Founder and CEO at Scope3, posted analysis on August 29, 2025, predicting the controversy could accelerate market consolidation and direct relationships. He forecasted that DSPs might go direct to supply because they cannot trust the programmatic supply chain to provide transparent information. His analysis anticipated major platforms developing proprietary solutions.

The statement from Prebid.org reaffirmed the organization's commitment to transparency, interoperability, and publisher choice. It positioned the upcoming update as ensuring flexibility and reducing confusion rather than reversing the August 2025 decision. Publishers will maintain control over whether to enable Transaction IDs and now gain additional control over which format to send.

The opt-in nature of Transaction IDs in Prebid remains unchanged. Publishers must actively choose to enable them—a decision based on their assessment of privacy concerns, commercial relationships with demand partners, and technical implementation considerations. The upcoming update adds another layer of choice for those operating on the latest version.

Industry observers note that the 1% adoption rate of the new logic provides Prebid.org with flexibility to modify the approach without disrupting most publishers. The gradual version adoption cycle that typically slows the spread of changes in this case provides time for the industry to assess different approaches and reach consensus on standards.

The situation illustrates governance challenges in open-source advertising technology development. With the IAB Tech Lab directly challenging a major implementation decision, the industry faces questions about how similar conflicts will be resolved. The balance between technical standards bodies and implementation platforms remains unresolved.

Demand-side platforms must adapt their auction analysis and optimization systems to function without reliable cross-exchange Transaction tracking where publishers implement SSP-specific identifiers. Buyers lose visibility into supply chain mechanics that influence auction dynamics and pricing. The removal affects their ability to implement sophisticated bidding strategies based on supply path evaluation.

For the marketing community, the Transaction ID situation demonstrates how technical implementation decisions can create substantial operational impacts. Publishers must evaluate version upgrade timelines while considering the implications of different Transaction ID configurations. Buyers face reduced transparency in environments where SSP-specific identifiers eliminate their deduplication capabilities.

The statement provides clarity that the majority of Prebid traffic continues operating under established Transaction ID mechanics. Publishers on earlier versions face no immediate pressure to upgrade or modify their configurations. Those who have upgraded to version 10.9 gain new flexibility with the upcoming release.

Prebid.org positioned its commitment to supporting the open internet and strengthening collaboration across the advertising ecosystem. The upcoming update represents an attempt to balance competing interests—publisher privacy concerns, buyer transparency demands, and technical standards compliance—through increased flexibility rather than mandated approaches.

The resolution of the Transaction ID controversy remains incomplete. The IAB Tech Lab's position that the implementation violates OpenRTB specifications stands in direct tension with Prebid's approach. Publishers, buyers, and technology providers continue navigating an environment where fundamental infrastructure operates under competing standards and interpretations.

Timeline

• June 2023: Prebid.js version 8 introduced support for Transaction IDs with opt-in configuration
• July 2025: Prebid.js version 10.0 released
• August 2025: Prebid Publisher Committee voted to modify TID handling to SSP-specific format
• August 27, 2025: IAB Technology Laboratory declared Prebid changes violate OpenRTB specification
• August 28, 2025: Michael Sullivan discussed impact on Marketecture Podcast
• August 2025: Prebid.js version 10.9 implemented SSP-specific Transaction ID logic
• September 18, 2025: Raptive proposed encrypted Transaction ID solution
• October 2, 2025: Trade Desk announced OpenAds platform and Prebid fork
• October 23, 2025: Prebid.org issued clarification statement on Transaction ID updates

Summary

Who: Prebid.org issued the statement, written by Garrett McGrath. The statement addresses publishers, demand-side platforms, supply-side platforms, and the IAB Technology Laboratory. The Prebid Publisher Committee made the August 2025 decision to modify Transaction ID handling.

What: Prebid.org clarified that Transaction IDs remain opt-in and announced an upcoming update allowing publishers using the latest Prebid.js version to choose between global or SSP-specific Transaction ID formats. The statement addresses confusion following the August 2025 implementation of SSP-specific identifiers in version 10.9. Currently, only 1% of Prebid traffic uses the new logic while 99% continues with the original global format.

When: The statement was released on October 23, 2025. The Prebid Publisher Committee voted on the modifications in August 2025. Prebid.js version 10.9 implemented the SSP-specific logic following the July 2025 release of version 10.0. The new update providing format choice will release this week according to the statement.

Where: The changes affect the global programmatic advertising ecosystem, particularly publishers implementing Prebid.js for header bidding. The situation impacts the open internet advertising infrastructure where Transaction IDs enable or prevent cross-exchange visibility for demand-side platforms.

Why: Prebid modified Transaction ID handling to address publisher privacy concerns and flexibility demands after some DSPs required TIDs as a condition for spend. The upcoming update aims to reduce confusion and provide flexibility to publishers while maintaining the opt-in policy that has existed since June 2023. The situation reflects tensions between publisher yield protection, buyer transparency demands, and technical standards compliance.