Amazon opened up its Prebid adapter for beta testing on January 21. The update brings Amazon demand directly into Prebid, the open-source framework publishers already use to manage competition across buyers. Now publishers, who have spent years trying to regain control of the ad auction, are testing to see if the changes deliver on that promise of better competition.
Previously separate auctions will be folded into the same bidding process. Amazon bids will now compete in real time alongside other buyers in Prebid (except Google), using the same audience and identity signals (like LiveRamp’s agentic audiences) and the same dynamic floor‑pricing logic that already govern the rest of the Prebid auction.
That shift promises real simplification for publishers juggling multiple JavaScript libraries and competing auction logic. But it also raises a question: How do publishers measure whether Amazon’s participation actually improves the auction?
We spoke to publishers about how they are testing Amazon’s Prebid adapter to answer those questions, and to see if a more consolidated auction delivers real net value.
Leveling the playing field
Until now, Amazon largely operated its own parallel ad auction alongside publishers’ Prebid setups, such as Amazon TAM (Transparent Ad Marketplace) for large enterprise publishers and Amazon Unified Ad Marketplace (UAM) for midsize publishers.
That meant Amazon demand often sat outside the same decision layer where publishers already managed competition, floors and signals across other buyers.
For Raptive, which manages advertising across thousands of publisher sites, those parallel auctions added real operational complexity. Patrick McCann, Raptive’s Senior Vice President of Research, said publishers typically juggle multiple heavyweight JavaScript libraries on the page – from Google and Amazon to Prebid and proprietary publisher tech – all of which need to pass signals and resolve bids on tight timelines.
“The more libraries you have, the more complex your setup becomes,” McCann said. “You end up with separate timers, separate logic, and effectively an ‘uber-auction’ trying to reconcile everything.”
Raptive has already begun early-stage testing of Amazon’s Prebid adapter on small slices of traffic, starting with display and then expanding to other formats. It’s still too early to draw conclusions on things such as bid density, win rates or clearing prices, McCann said, but the infrastructure shift alone is meaningful.
Unwind Media plans to test Amazon’s Prebid adapter in the near future by comparing how Amazon demand performs inside Prebid versus within Amazon’s existing standalone auction setup, said Emry Downinghall, SVP of programmatic revenue for the web-based gaming company that develops card and puzzle games.
By running Amazon in both environments, Unwind can evaluate the impact on the overall auction rather than isolating a performance change to a single partner like Amazon.
Testing for net value
When Unwind tests, it will measure how often Amazon submits bids, how often those bids win, and how much revenue Amazon contributes when running inside Prebid. But performance alone isn’t the point.
“The most important question is whether Amazon’s participation in Prebid adds net value to the auction,” Downinghall said. Net value means whether Amazon’s participation leads to higher overall yield after fees and auction effects and whether it introduces new demand rather than cannibalizing bids already flowing through Prebid.
Raptive’s evaluation will focus on how bids behave once they’re visible inside the same framework as other demand. Once Amazon’s bids are exposed inside Prebid, Raptive can see and score them alongside every other bid instead of treating Amazon as a separate black box, added McCann. That visibility lets Raptive tune its floor prices based on real Amazon demand and weed out low‑value bids, which, he argues, makes the whole auction more efficient.
What publishers are testing for, he added, isn’t whether Amazon bids aggressively, but whether its participation improves overall auction clearance.
Signals, simplification and what comes next
Prebid is typically the first place publishers introduce new identity and audience signals – whether that’s LiveRamp, first-party segments or other user data – before determining whether and how to extend those signals elsewhere, said McCann.
When Amazon demand sits outside that framework, publishers often have to duplicate work to ensure key signals reach one of their most important buyers. If publishers switch to receiving Amazon demand through Prebid, they won’t have to go through that extra step – a small but meaningful reprieve for publishers looking for efficiency gains.
