Inside the Prebid Summit, the sell-side argues with itself about Google and Apple

At the Prebid Summit in New York, a working group on how a Prebid ad server might integrate with Google Ad Manager descended into boisterous cross-talk that Microsoft Advertising engineer Brian Sardo, pitching the group's version, welcomed as the point of the exercise, while Prebid board chairman and OpenX CTO Joel Meyer's alternate proposal lost out. Raptive SVP Patrick McCann, chair of Prebid's JavaScript working group, noted Googlers in the room, and the group seriously debated whether Prebid should prepare for GAM to evade Judge Brinkema's remedies, with IAB Tech Lab's Hillary Slattery pressing a server-side overhaul and the lab's Trusted Server tech. The iOS 27 spectre hung over the main stage: MediaWallah chief business officer Ryan Teshima-McCormick said LiveRamp and ID5, both on the panel, were among those unconditionally blocked by Safari WebKit. "For everyone in this room that's been trying to understand and manage their data partnership strategies, specifically as it pertains to signals, while literally the ground is moving under our feet," Teshima-McCormick said. In the bluntest moment, Scope3 CEO Brian O'Kelley lit into The Trade Desk for having "f*

ing forked" Prebid a year ago: "Thank you for not contributing. Thank you for trying to split off your own motivation and do something worse for this community." TTD's Mike O'Sullivan demurred and pivoted to the DSP's publisher-side contributions.

The crux:

The open-source sell-side is using the Prebid Summit to decide, in public and at speed, how to rebuild itself after the twin shocks of the Google remedy and Apple's iOS 27 blocklist, and the fault lines, buy-side versus sell-side, TTD versus everyone else, are fully on display.

Sell-side read:

When the buy-side's largest independent DSP is publicly accused of forking the publisher's open-source wrapper, and Apple is blocklisting identity vendors by domain, the safe default for a publisher is control of its own auction logic and first-party data, because neither the DSP layer nor the browser layer can be trusted to protect your yield.

Watch:** whether TTD responds substantively to the fork criticism and whether Apple's blocklist, which Aditude says has already cut Safari eCPMs 10.5% among updated users, expands to a broader slate of ad tech and data vendors before the end of October.