After backlash from The Trade Desk and others, Prebid.org clarified how Prebid.js handles Transaction IDs — a core signal for tracking and comparing bid requests across the programmatic supply chain.
The latest flashpoint bubbled to the surface this summer when Prebid issued a change that rendered TID non-unique across exchanges, effectively undermining its primary purpose of helping buyers detect duplicate bid requests.
The change was initially rolled out with little public notice, but concerns about governance and influence in open-source standards were soon raised — it’s fair to say that since the August update, there’s been much (public) spirited debate on the matter.
What happened?
The Prebid update, introduced in version 10.9, made TIDs specific to supply-side platforms rather than global — a shift that demand-side platforms claimed would undermine transparency, making it harder for them to detect duplicate requests.
The Trade Desk was arguably the most vocal critic of the August update — which proposed giving each bidder a unique TID per auction rather than a single shared TID — claiming that it would undermine supply-path transparency and deduplication. In fact, many interpreted The Trade Desk’s launch of OpenAds as a riposte to Prebid’s 10.9 proposals, although the timing of its formal September launch would suggest its plans were in place for some time before the August update.
Prebid, however, maintained that the proposed change was approved by its publisher committee to give publishers more control and flexibility, not to benefit resellers, as some DSPs were making TID availability compulsory for continued trading.
What’s happening now?
More recently, Garrett McGrath, a Prebid board member who also serves as svp of product management at leading SSP Magnite, has since moved to clarify its TID updates “following industry discussion and some confusion around implementation timelines and adoption.”
In an October 23 blog post, he wrote, “To ensure flexibility and reduce confusion, Prebid.org will release an additional update this week allowing publishers using the latest version of Prebid.js (and who have opted to pass TIDs) to choose whether to send global or SSP-specific TIDs. All earlier versions of Prebid.js will remain unchanged, continuing to send a single global TID when enabled.”
McGrath further stressed that TIDs remain optional and that the project continues to prioritize transparency, interoperability, and publisher choice, framing the compromise as an effort to cool a growing divide between the buy and sell sides over how open-internet auctions should be governed.
For the industry’s buy-side, the shared TID served as a core signal for detecting duplicate bid requests, comparing paths, and ensuring efficient auctions, i.e., supply-path optimization. With the proposed version 10.9 approach, buyers lose visibility into whether multiple bid requests stemmed from the same impression, raising costs and reducing optimization capabilities.
However, according to Prebid’s official numbers, only about 1% of traffic uses the new TID logic, as most publishers haven’t upgraded to the latest version, with parties there characterizing its efforts since August as an attempt to meet buy-side requests, while sustaining their own business interests.
A rollback?
The debate remains over whether the latest Prebid position constitutes a U-turn or a “rollback,” as several sources, all of whom requested anonymity to maintain relationships, characterized the situation to Digiday. For its part, Prebid maintains that the latest development is simply a clarification, as the update will provide optionality.
In conversation with Digiday, leading industry SPO expert Chris Kane, CEO of Jounce Media, noted that TID adoption among publishers may not be as widespread as many think, while emphasizing the need for sell-side players to ensure greater harmony in the industry’s ecosystem.
“The number one priority for sell-side technology companies must be building buyer trust in RTB auctions because there is now a very real opportunity for buyers and their DSPs to bypass SSPs entirely,” he added. “It’s hard to name a major DSP that does not have scaled publisher-direct integrations.”
Meanwhile, Gareth Glaser, cofounder and CEO of Gamera, who formerly served as the chair of Prebid’s project management committee, told Digiday, “Anytime one of these organizations or one of these systems introduces additional choice and additional transparency, that’s always good… Prebid has added something back in that gives publishers more choice and provides the framework for more transparency.”