Publishers implement modifications to Prebid transaction IDs in response to yield preservation worries

In a recent turn of events, the IAB Tech Lab has accused Prebid of materially violating the OpenRTB specification with its recent changes to transaction ID implementation. This controversy, which emerged from a heated LinkedIn discussion, has exposed fundamental disagreements about programmatic advertising's future structure and highlighted broader challenges in balancing transparency, privacy, and technical standards.

The controversy was initiated by Mike O'Sullivan, co-founder of sincera, and quickly gained traction. Heather Carver, Chief Revenue Officer at Freestar, provided the most comprehensive publisher perspective in the thread. The official Prebid.org response revealed five specific risks that motivated the implementation changes.

The IAB Tech Lab, led by CEO Anthony Katsur, publicly stated on August 27, 2025, that the implementation of transaction ID changes by Prebid.org constitutes a material violation of the OpenRTB specification. The technical modifications affect three core areas of Prebid's implementation, eliminating the cross-exchange visibility that the OpenRTB specification originally intended to provide.

Publishers using Prebid Server integration face particular challenges due to these technical modifications. The changes have raised concerns about identifier linking, a practice that some publishers have used as a strategic advantage in opposing transaction IDs. The W3C's fingerprinting guidance documentation further fuels these concerns.

The controversy could provide regulators with additional evidence of market dysfunction requiring intervention as the industry approaches $700 billion in annual ecosystem value. The Prebid decision represents a fundamental power shift within the programmatic advertising supply chain.

One potential solution might include optional transaction ID scoping, publisher-controlled identifier policies, or enhanced privacy controls within existing frameworks. The IAB Tech Lab has announced plans for a dedicated forum to address the transaction ID controversy.

Meanwhile, The Trade Desk has been actively promoting transaction ID adoption among publishers, emphasising its critical functions for advertiser campaign efficiency and cost management. Transaction ID deduplication is a key aspect of this, ensuring that the same user isn't counted multiple times across different exchanges.

The right path forward, according to the IAB Tech Lab, is to work collaboratively on the OpenRTB specification, rather than bypassing or reinterpreting it. This controversy serves as a reminder of the importance of maintaining standards and transparency in the ever-evolving world of programmatic advertising.

Publishers implement modifications to Prebid transaction IDs in response to yield preservation worries