Last look was a feature of Google's publisher ad server, DoubleClick for Publishers (DFP, now part of Google Ad Manager), that allowed Google's own ad exchange, AdX, to see the highest competing bid for an impression and then bid after every other exchange had committed its price. In a sealed auction no participant sees rivals' offers. This feature lifted that protection for one bidder. In her April 2025 liability opinion, Judge Leonie Brinkema wrote that "Last Look was another anticompetitive policy that entrenched Google's monopoly power".

Timing was the point. Publishers had turned to header bidding, a technique that lets several exchanges bid at once before the ad server is called, to stop one exchange holding a privileged position. Last look sat behind that auction and gave Google a second chance. Google's stated defence, as the court summarised it, was that first look and last look raised revenue for publishers and gave advertisers more chances to bid. The court rejected that justification for both features. According to the opinion, some Google employees viewed header bidding as an existential threat to the company's ad tech business.

The term applies to open-web display, which the court defined as display ads on websites that use third-party ad tech infrastructure to match advertisers' ads to publishers' inventory.

How it worked, step by step

The flow below follows the court's findings of fact, which draw on trial testimony and Google documents.

  1. A publisher runs a header bidding auction. Exchanges submit bids through a wrapper such as Prebid.js, and the highest bid wins that stage.
  2. To compete with AdX inside DFP, the publisher had to pass that winning header bid into the ad server as a price floor, according to the opinion.
  3. DFP then gave AdX the chance to adjust its own bid in response to the highest bid from rival exchanges.
  4. AdX, knowing the number to beat, could "just bid 1 cent more", in the words the court recorded from PubMatic's Rajeev Goel. If it did, AdX won the impression.

An illustration, not taken from the record: a header bidding exchange submits $2.00 as its top bid. AdX, seeing that figure, needs only $2.01 to win, whatever its advertisers might have been prepared to pay in a blind auction. The rival exchange never gets to respond.

A second mechanism compounded the effect. Under sell-side dynamic revenue share, AdX varied its fee impression by impression. The court found it charged 15 percent or less on competitive impressions and 25 percent or more on less competitive ones, while holding an average of about 20 percent. Last look supplied the information that made such pricing possible, because third-party exchanges could not see all the bids and so could not vary their own fees the same way.

On the sell side, the operator was Google itself, acting through DFP, which held over 90 percent of the publisher ad server market according to the court. On the buy side, advertisers reaching AdX through Google's buying tools benefited, while advertisers using non-Google demand-side platforms (DSPs) were disadvantaged. The European Commission described the same pattern: DFP told AdX in advance about competitor bid values, as PPC Land reported on the Commission's September 5, 2025 decision.

Origin and evolution

The groundwork was laid by dynamic allocation, which arrived with the DoubleClick Ad Exchange on September 18, 2009. It let the exchange compete in real time against booked demand inside the ad server. First look followed in 2010, giving AdX the first opportunity to buy any impression before other exchanges, according to Index Exchange's November 10, 2025 complaint.

Header bidding emerged as a workaround, and last look was the answer to it. Teads alleges in its August 3, 2026 complaint that last look operated from 2014 to 2019. Prebid.org, the open-source header bidding project, launched on September 11, 2017 with 81 demand partners.

Sources differ on how and when last look ended. In March 2017, AdExchanger and others reported that Google was moving away from it; Jonathan Bellack, a Google director of product management, told The Drum that Google was collecting each exchange's price and "putting it in a unified auction where the highest price wins". That change was tied to Exchange Bidding, Google's server-side alternative to header bidding, later renamed Open Bidding. The court record, by contrast, dates the elimination to 2019. In March 2019, Google announced a unified first-price auction for Ad Manager, and Jason Bigler, its director of product management, said Google would "no longer have a 'last look' opportunity", according to MarTech. PPC Land recorded the rollout as complete on September 5, 2019.

The 2019 change came with a trade-off. On May 10, 2019, Google introduced unified pricing rules, which barred publishers from setting higher floors for AdX than for other exchanges. The court found that Google presented the two changes as consistent with each other, while publishers had used differential floors to reduce their dependence on Google.

Why it matters to marketers

For advertisers, last look affected which exchange won an impression and what the publisher earned from it. A fee that averages 20 percent but swings between 15 and 25 percent by impression is hard to audit from a campaign report. Advertisers buying through rival exchanges lost auctions they might otherwise have won.

The practice sits at the centre of several legal actions. The Commission fined Google EUR 2.95 billion and, in a public version of its decision released in January 2026, described last look and dynamic allocation in detail. Index Exchange sued in Virginia, and Teads followed in the Southern District of New York (Case 1:26-cv-06591), citing 6.88 trillion impressions it says were lost to rival exchanges. PPC Land's entry on self-preferencing groups last look with first look and dynamic allocation.

Limitations, criticisms and open disputes

Google's position has been that its ad tech features served publishers. The court accepted a narrow part of that argument: some aspects of dynamic allocation, such as adding AdX as a new demand source and enabling real-time bids, did raise publisher revenue, and the plaintiffs did not call those aspects anticompetitive. Last look did not receive the same treatment. Three plaintiffs' experts testified that it was anticompetitive, according to the opinion. Google has said it intends to appeal the liability finding, according to a Tech Policy Law summary of the remedies order.

Disputes remain about whether last look truly ended. Teads alleges that a 2019 mechanism called Minimum Bid to Win, which told authorised bidders the second-highest price, was "last look reconstituted after the fact". That is an allegation in a complaint, not a finding.

Sources also disagree on when last look started, when it ended, and how far the 2017 changes went. Evidence from Google's own staff complicates the picture of 2019: an August 2019 message from Lindsay Pursell, quoted by AdExchanger, said Rubicon and the wider Exchange Bidding community had seen spend fall since the first-price and unified pricing changes. Removing last look, on that evidence, did not by itself restore rivals' share.

Scope is a final limit: the prohibitions apply to programmatic open-web display only.

Not the same as

First look is the mirror image. It gave AdX the first chance at an impression before other exchanges saw it, while last look gave AdX the final chance after them. The court treated both as parts of the tie between DFP and AdX.

Dynamic allocation is the broader Ad Manager feature that lets non-guaranteed demand compete with guaranteed line items in real time. PPC Land's DFP entry distinguishes it from the conduct built on top of it. The court identified first look, not real-time bidding itself, as the anticompetitive element.

Header bidding is the pre-auction technique rivals used to bid together. Last look was an advantage in the step after it, not a part of header bidding.

Last look in foreign exchange (FX) is a separate practice with the same name. There, a liquidity provider holds a trade request for a short window before accepting it. The Global Foreign Exchange Committee published revised guidance on the topic, under Principle 17 of the FX Global Code, on December 19, 2017.

Recent developments

On September 2, 2026, Judge Brinkema declined to order a sale of AdX and instead accepted behavioural remedies. The ruling prohibited first look and last look on open-web display inventory and ordered unified pricing rules deprecated. Google was also barred from reimplementing either feature. The decree runs for six years, applies worldwide, and takes effect 60 days after entry. Google had already removed unified pricing rules in December 2025. The April 2025 opinionhad condemned five practices, last look among them, and the liability coverage records it as one of the features the court examined.

Digital Content Next, a trade body for publishers, argued that Google must now deliver the fixes it promised. The remedies also require Google to connect AdX to Prebid. PubMatic chief executive Rajeev Goel said on September 17, 2026 that Google estimated roughly a year to 15 months to build it. The order also applied functional equivalence, meaning that access given to rivals must perform as well as the access Google gives itself.

The details are still being settled. According to AdExchanger, Google and the Department of Justice filed competing proposed final judgments on October 5, 2026. The US Department of Justice (DOJ) proposal seeks the AdX-Prebid connection within six months, against twelve for Google, and both sides accept that first look and last look cannot be reimplemented. As of October 2026, no final judgment has been entered.

Timeline

  • September 18, 2009: DoubleClick Ad Exchange launches with dynamic allocation.
  • 2010: First look is introduced through dynamic allocation, according to Index Exchange's complaint.
  • 2014: Teads alleges last look begins operating.
  • March 31, 2017: AdExchanger reports Google is abandoning last look in favour of a unified auction tied to Exchange Bidding.
  • September 11, 2017: Prebid.org launches with 81 demand partners.
  • March 2019: Google announces a unified first-price auction for Ad Manager and says it will end last look.
  • May 10, 2019: Google introduces unified pricing rules.
  • September 5, 2019: The first-price rollout is completed.
  • April 17, 2025: Judge Brinkema issues the liability opinion in United States v. Google, finding last look anticompetitive.
  • September 5, 2025: The European Commission fines Google EUR 2.95 billion over ad tech self-preferencing.
  • November 10, 2025: Index Exchange files suit against Google.
  • December 2025: Google removes unified pricing rules from Ad Manager.
  • August 3, 2026: Teads files suit in the Southern District of New York.
  • September 2, 2026: Judge Brinkema orders behavioural remedies, barring first look and last look on open-web display.
  • September 16, 2026: The full remedies decision is unsealed.
  • October 5, 2026: Google and the Department of Justice file competing proposed final judgments, according to AdExchanger.

Summary

Who: Google, through its publisher ad server DFP and its exchange AdX, was the operator. Publishers, rival exchanges such as Index Exchange and PubMatic, and advertisers using non-Google DSPs were affected. Judge Leonie Brinkema and the European Commission were the main decision makers.

What: Last look let AdX see the highest competing bid and bid after every other exchange, in an otherwise sealed auction. Courts and regulators found it anticompetitive.

When: Sources place its operation between 2014 and 2019, with changes reported in 2017. The US liability opinion came on April 17, 2025, and the remedies order barring it on September 2, 2026.

Where: In DFP's auction logic for open-web display inventory, with the legal fights in the Eastern District of Virginia, the Southern District of New York and before the European Commission.

Why: Google built it as header bidding threatened AdX's position. Its removal is a central part of the effort to restore equal competition between exchanges.