Prebid.org has established itself as a respected open-source software maker and standards-setter in online advertising. It has the necessary scale, leverage and momentum to help shape programmatic trading and drive interoperability across the ad tech ecosystem.
Now begins the hard part.
Prebid stands at a major inflection point for itself and the open web.
Across the supply chain, stakeholders are jockeying to shape Prebid’s future as they await a decision in the DOJ v. Google ad tech antitrust case. Both sides propose remedies that include a Prebid integration – meaning that, regardless of how the court rules, a major portion of the web could soon open up to its code.
Prebid must also balance its growth alongside parallel efforts by other industry groups – namely, the IAB Tech Lab, long regarded as the standards-setting authority for programmatic advertising – as the two increasingly move down separate paths.
A little history
The root of these tensions can be traced back to 2017, when Prebid was founded and Google blocked Prebid’s nascent open-source software from merging with the IAB Tech Lab.
During the liability phase of the DOJ v. Google ad tech antitrust trial in Virginia last year, the government played a videotaped deposition with Brian O’Kelley, the founder of AppNexus and its former CEO, who revealed that the Prebid header-bidding tech – which originated at AppNexus in partnership with other SSPs – was offered to the Tech Lab to operate. The Tech Lab was a natural landing place for header-bidding standards.
But Google nixed that move. (Thanks to the trial, we now know that Google’s stance was part of its wide-ranging effort to stamp out adoption of header bidding, since the practice undercut Google’s advantages in the publisher ad tech market.)
Prebid was then forced to chart its own course, and, over time, the small group of backers and product managers devoted to the open-source product proved its viability.
“There was clearly a need for Prebid back in 2017, when you look at the trajectory from where it started to where it is today,” Garrett McGrath, Magnite’s SVP of product management and a Prebid board member, told AdExchanger.
Yes, the industry needs a group that ruthlessly pursues standards, he said, which is the Tech Lab. But the industry also needs an open-source software org, he added, “as evidenced by the rise of header bidding” and “everything else” that Prebid has developed.
Prebid isn’t displacing the Tech Lab, McGrath said, because the industry requires both.
Prebid in practice
Prebid and the IAB Tech Lab have, for the most part, worked effectively side by side, with one producing standards and the other software.
But the two orgs aren’t perfectly complementary. Prebid operates an industry standard in header bidding. The Tech Lab would like to produce code.
Consider, for example, the question of which industry org should be responsible for the much-needed standards that will govern how publishers and ad tech companies use LLMs and agentic AI systems across programmatic advertising. The Tech Lab already began work on an LLM Content Ingest API initiative this year and launched an AI Content Monetization Protocols Working Group in August.
But Prebid might also produce code for those use cases. And there is already a new open-source standards org called the Ad Context Protocol, which launched this month as a self-described “Prebid-type layer” for agentic advertising applications in advertising, one of the founding board members, PubMatic CRO Kyle Dozeman, told AdExchanger.
The phenomenon of parallel open-source industry groups is not unheard of. In 2023, for example, Kevel created an outside working group dedicated to retail media standards to help speed up the pace and urgency of the IAB Tech Lab’s retail standards working group. Kevel’s group was eventually incorporated into the Tech Lab proper.
But Prebid and the Tech Lab are truly separate – and, at times, even conflicting – industry bodies.
Even so, it’s not impossible that Prebid could eventually be folded into the IAB.
The Tech Lab actually made overtures to merge with Prebid in 2021 after Anthony Katsur was named CEO of the Tech Lab with a self-proclaimed mandate to accelerate new product development and decentralize power within the org so the big platforms could no longer hamstring its operations.
By then, though, Prebid was firmly on its feet and liked being independent.
“There are big advantages in making binary decisions: Do we produce code that does X, or not?” one Prebid board member recounted to AdExchanger last year. “It’s pretty nice not to be tangled up in questions of policy.”
Heather Carver, CRO of Freestar and a Prebid board member, told AdExchanger, also last year, that being independent from the IAB means Prebid can act with greater focus on behalf of the supply side, free from bureaucratic obstacles.
“Call it ‘move fast and fix things,’” she said.
Prebid now
But what does it mean in practice to “move fast and fix things”?
For a salient example, think back to August, when Prebid surprised the programmatic industry by suddenly updating its system to assign unique transaction IDs (TIDs) to each bidder instead of sharing the same ID across all participants.
DSPs rely on TIDs, which are OpenRTB identifiers, because the data is consistent across publishers and SSPs. The IDs can’t be used to target or track an individual as with third-party cookies. But when TIDs are consistent on the supply side, DSPs can use them to avoid bidding multiple times on a duplicated impression.
The Trade Desk pushed back hard on Prebid’s move. Earlier this month, TTD announced its own forked version of the Prebid code, called OpenAds, which requires sharing TID data, and presented it as an effective way to attract demand from its advertisers.
McGrath told AdExchanger that TTD’s forked version of Prebid does not represent a rift within the Prebid board, nor is it unique. Other Prebid members also create their own exclusive products based on the main Prebid branch.
However, those efforts added new functionality instead of reversing core Prebid updates.
Responding to the debate, Prebid announced an update last week allowing publishers using the latest version to continue sending TIDs to specific SSPs if they choose, a compromise meant to balance publisher control with The Trade Desk’s call for default sharing.
On stage at the Prebid Summit in New York City in mid-October, Jeff Green, The Trade Desk’s CEO, noted that its forked version of the Prebid code is actually the same as Prebid’s – “just from a few weeks ago.”
But Prebid’s rapid pace of innovation means that just a few weeks ago can feel like an eternity.
For example, Prebid 10 was released on July 1, bringing significant improvements, including native support for programmatic audio ads, dynamic creative and a Chrome browser AI module that uses the Gemini “summarize this web page” feature to beef up the metadata in an ad call.
Prebid 10 also addresses serious problems with the previous version, such as a bug with the PUC (Prebid Universal Creative) rendering script and an in-SafeFrame rendering issue.
These updates and security fixes were discussed in detail during developer-focused sessions at the Prebid summit, and the engineers in the room did not hold back.
“Don’t use PUC!” one Prebid product leader admonished the room.
Another person, meanwhile, called out that, yes, these are cool new features, so shouldn’t they also be included in Prebid 9? Most publishers are still using that version, he said.
“No!” retorted the same product leader. Prebid 9 is not adding new features. The org’s focus is to continue working on Prebid 10, he said, not make Prebid 9 more appealing.
Why tell this anecdote? It’s evidence of how fast Prebid changes.
Prebid’s TID update, which had immediate and important ramifications for the entire ecosystem, happened essentially overnight.
The Trade Desk was caught by surprise, despite its board seat, and the update wasn’t communicated to the IAB Tech Lab ahead of time. Tech Lab CEO Anthony Katsur posted on LinkedIn afterward that Prebid’s update to TIDs was “materially noncompliant with the OpenRTB specification,” among other fighting words.
So Prebid moves fast, but it also breaks things. At least from the IAB Tech Lab’s perspective.
Prebid, for its part, responded to AdExchanger that the TID update “was unintentionally pushed live early due to a clerical error in the release process, and this was communicated to Tech Lab.”
An industry in flux
But Prebid is coming of age at a wild time.
Although nobody knows what Judge Leonie Brinkema’s decision will be in the DOJ v. Google ad tech case, it’s likely that the ruling will include some requirement for Google to support Prebid or develop its own Prebid wrapper.
However, as Prebid’s importance grows, so do the pressures that come with being a powerful industry group.
For example, Prebid must now reckon with a key question: Who is it for?
The org was created by a hybrid SSP/DSP – AppNexus – and has been championed by SSP partners and publishers as an open-source product.
As an independent entity, Prebid took on the role of representing publishers and the supply side – a mantle that had been largely abandoned by the IAB years earlier. The IAB was originally founded as a publisher org but gradually expanded to include – or was co-opted by, depending on your point of view – first publisher ad tech, then demand-side ad tech, then the big walled garden platforms and, eventually, brands.
Prebid’s code is now “in pretty much every corner of the industry,” McGrath said, and the organization now has a “buyer task force,” not to mention TTD joining the board in 2022 and more recent agency holdco partnerships. Although, he added, the primary thing the organization does is produce header bidding tech, which means it is “first and foremost for publishers.”
Someday, though, and perhaps even soon, publishers and their tech partners may be first, but not so much foremost, within Prebid.
Prebid’s supply-side roots are important, Green said during his Prebid Summit keynote. The group, he said, had “risen from the rubble, from the ashes” of Google’s effort to stamp out header bidding as a democratizing force for the entire ecosystem.
“But we are at a crossroads,” he added. “We have to decide what this is going to be and what are our constituents going to be.”
Green’s point is that the organization should represent a wider constituency.
Aside from TTD, however, which is the sole buy-side representative on the Prebid board, there’s little consensus about how Prebid should evolve or even whether it should be an independent organization in the long term.
One board member told AdExchanger on background that they still think it makes sense for Prebid to be part of the Tech Lab and someday will likely end up there. A different Prebid board member, however, also speaking anonymously, referred to the IAB’s evolution from a sell-side group to a universal trade org as a “waking nightmare” to be avoided at all costs.
In other words, where Prebid goes from here is truly an open question.
What happens next?
Although Prebid has achieved impressive adoption, a large portion of the web – including many sites that default to Google Ad Manager, Google’s supply-side platform – still don’t use Prebid code. Prebid also faces the ongoing challenge of getting its publisher base to upgrade to the latest version. Adoption is not a one-time thing; it’s an ongoing commitment.
Most sites still use the old Prebid, and vendors can’t test the cool new functionality of Prebid 10 until those sites upgrade – which they are typically slow to do.
Prebid doesn’t force publishers to upgrade or adopt, the org’s president, Michael Racic, told AdExchanger. The group makes improvements to the current version, and when publishers want those features, they adopt. For-profit companies may force-shift updates, he said, but that’s not the Prebid model.
As one extreme example, Racic pointed to a “healthy debate” earlier this year within Prebid about whether to retire the Prebid 6 code, which still has a few hundred publishers that never upgraded. They’re still using Prebid 6, btw.
Prebid may take a laissez-faire stance with publishers. But it’s hard to see how Prebid can keep growing without clashing more frequently with other industry bodies.
Recall that Tech Lab CEO Katsur’s post on LinkedIn that Prebid’s August update to TIDs was “materially noncompliant with the OpenRTB specification.”
McGrath and Racic said there is no animosity between Prebid and the Tech Lab and that there are open lines of communication between the two organizations. “At least from our side,” Racic added.
The TID update was the “one specific thing in the history of this org” when the two groups had a public issue, he said.
Although, that TID update was a very big deal.
Two people who are members and contributors to both the Tech Lab and Prebid told AdExchanger that the TID update revealed a major governance divide between the two orgs. The IAB Tech Lab would never push out a new update overnight that directly affected online ad performance and everyday work in the industry as Prebid had, they said.
“It literally couldn’t happen,” the same source said, citing Tech Lab working group bylaws that require approvals from many cross-industry stakeholders before a proposal moves forward.
Also, on the gossipy side, both sources confirmed that the Tech Lab’s Slack account was unceremoniously removed from Prebid’s Slack channel since the TID drama began.
“I thought initially it was the Tech Lab leaving out of spite,” one source said. Turns out, The Tech Lab account had been booted.
Prebid responded that its Slack is open only to members, and that the Tech Lab had been included in only one channel for a joint project involving feedback on the Chrome Privacy Sandbox. That channel was disabled because the project no longer exists, so the Tech Lab’s removal from the Prebid Slack had nothing to do with the TID drama and LinkedIn kerfuffle weeks later.
But Prebid’s challenges go beyond dustups on LinkedIn and Slack drama.
In breakout discussion groups during the Prebid Summit, participants emphasized how issues like publishers sticking with old Prebid versions, the rising cost of Prebid testing and The Trade Desk channeling demand through its own sell-side integrations have negatively impacted the ability to scale up campaigns and testing for Prebid.
One ad tech exec who contributes to Prebid and the IAB Tech Lab told AdExchanger at the event that they were in a silent fury all day, frustrated by the on-stage bombast and product announcements, such as a publisher LLM and agentic API product and advocacy that directly undercut the Tech Lab’s work.
Rather than a single boat with rowers pulling in one direction, they said, there are now multiple boats going in multiple directions. Which raises an important question: Can a coalition made up largely of supply-side ad tech companies keep this ecosystem moving forward together?
Just ask The Trade Desk. The whole industry is vying to influence Prebid right now, and TTD has opinions.
“If it’s just resellers,” Green said during his Prebid Summit keynote, using a technically correct term for supply-side vendors that publisher ad tech execs despise, “this will be a very different group than if we’re representing resellers, sellers, publishers and buyers: everybody.”
