Ad Tech Briefing: Can flipping the ad auction wrest control of ad tech from Google?

Of course, that was the main point of debate at the most recent U.S. antitrust trial involving Google, where the presiding judge stopped short of ordering a divestiture of Google Ad Manager assets and instead insisted that it integrate with Prebid’s tech. 

Digiday sources claim the proposals are not concrete yet, but the early buds of its proposals were previewed at the New York City event; AdExchanger first reported the pre-brief, and, if realized, it would essentially turn a key piece of programmatic advertising on its head.

Separating GAM and AdX

Currently, Prebid runs its auction and passes the winning bid to an ad server (usually Google’s GAM), where it competes against demand from Google’s AdX. However, the new proposal reverses that order: ad servers would bid into Prebid, with sources telling Digiday the proposals previewed at the Oct. 13 event are awaiting final sign-off after a period of public consultation.

To many, this may sound like dry details, or “plumbing,” to quote industry parlance, but much of the power in programmatic advertising lies in those details.

Under the model, publishers could potentially access demand from AdX without making Google’s ad server the place where the final competition occurs. Instead of Prebid sending a winning bid into GAM, GAM — and potentially other ad servers — would send bids into Prebid, changing both the sequence of the auction and the information available to the companies participating in it.

For those that need a refresher, Google’s ownership of both GAM and Google’s ad exchange, a.k.a. AdX, has long been at the center of complaints about how the programmatic auction operates.

Under the current arrangement, the winning Prebid price enters GAM before AdX competes against it; reversing the flow would put AdX into an auction controlled outside Google’s ad server, essentially separating AdX and GAM without requiring Google to divest either one.

Prebid is targeting early 2027 for formalization rather than promising an immediate rollout, and Google has not committed to implementing Prebid’s preferred architecture, with sources at the conference claiming Google has already attempted to “claw back” some of the provisions ordered by the courts.

Too little too late? 

But the proposal illustrates a broader shift underway in ad tech, i.e., companies outside the largest platforms are increasingly trying to move the point at which decisions get made in a bid to insulate themselves from the policy whims of players such as Apple and Google — the recent uproar over Apple’s iOS 27 changes, and the implementations for ad targeting within Safari are a painful reminder of this need, for many.

However, as others have already asked, is this too little, too late, especially as we move to agentic systems?

Elsewhere last week, and away from the mechanics of programmatic advertising, Google offered an olive branch to Madison Avenue’s buy-side, telling advertisers who want more say over automated systems that they can “say goodbye to all-or-nothing channel targeting.”

On Oct. 14, Google rolled out optional channel prioritization and budget allocation controls across Search, Shopping, Performance Max, and Demand Gen. Advertisers can designate higher-priority channels to receive budget first and cap what goes to secondary channels, rather than handing the entire allocation decision to Google’s automation.

Of course, Google is pitching such developments as giving advertisers more levers around the automation of its systems, but those experienced industry observers will have a long list of horror stories as to why continued vigilance is essential. 

In summary, these developments point to three parallel trends: Prebid wants to change who runs the auction, Google is giving advertisers more control — or appears to — over how its automated machinery allocates money. Meanwhile, the iPhone-maker can disrupt the whole Apple cart (pun intended) and alter the economics of the whole exercise with a software update.

So, while the mechanics of programmatic advertising may be getting rewritten, the real levers of control remain concentrated at a handful of critical points; Prebid’s latest proposal attempts to chip away at one of them, but whether Google agrees to move with it is another question.

Numbers to know

Findings from the latest WARC analysis:

5.5%: Combined advertising-to-sales ratio among 25 of the world’s largest brands in 2025, down from 6.1% in 2019.

56%: Increase in combined advertising expenditure among those 25 companies between 2019 and 2025.

$52 billion: Additional advertising expenditure Alphabet, Netflix, Meta and Microsoft would have generated had they maintained their combined 2019 ad-to-sales ratio.

36%: Growth in collective advertising expenditure among consumer goods companies between 2019 and 2025.

What we’ve covered

⁠For some publishers, agentic advertising is still a question of ROI

Agentic buying dominated Advertising Week conversations, but publisher executives remain wary of investing heavily before the technology demonstrates measurable returns.

⁠OpenAI moves to make ChatGPT Ads more measurable — and more visual

OpenAI is adding visual formats and expanding measurement as it attempts to move advertiser budgets beyond the experimental stage.

What we’re reading

⁠New ‘zero-click’ spyware hacked phones using targeted ads

Research from Citizen Lab and Confiant details how online advertising infrastructure was allegedly used to target devices with spyware without requiring victims to click an ad.

⁠Prebid’s proposed auction overhaul would do what the court wouldn’t: Separate AdX from GAM

Prebid wants ad servers to bid into its auction rather than the other way around, potentially giving publishers access to AdX demand without requiring Google’s ad server to run the final auction

Many of the world’s biggest brands have reduced ad spend as a proportion of sales, research finds

Big tech companies have seen their revenues rapidly increase but have not invested in advertising at the same rate, research from WARC finds.