When Apple shipped App Tracking Transparency in 2021, forcing an explicit prompt before any app could track a user across other apps, the effect showed up almost immediately in a competitor's earnings call: Meta later attributed roughly ten billion dollars in lost 2022 ad revenue to the change. That was the preview of what happens industry-wide once individual-level tracking stops being the default, well before Chrome made any decision of its own.
Google spent 2024 backing away from its own plan to fully deprecate third-party cookies, replacing outright removal with a new user choice experience in Chrome instead — a reversal that drew criticism from privacy advocates who had spent years preparing for the cookie's actual death. But the Privacy Sandbox infrastructure built for that transition, including cohort-based targeting through the Topics API, kept shipping regardless, because the underlying pressure — browser restrictions elsewhere, regulatory scrutiny, and Apple's example — never went away just because Chrome hedged on the deadline.
The emerging approach clusters people into cohorts based on shared browsing patterns rather than tracking individuals, or pushes matching onto the device itself so raw behavioral data never leaves the browser in identifiable form. Instead of an advertiser knowing a specific person visited a specific set of sites, it learns that a group with similar patterns exists and aims at the group.
Platforms with a durable first-party relationship — a logged-in account, a payment method on file — are far less exposed to any of this than the smaller ad networks and independent publishers who relied on handing a third party enough identity signal to make cross-site targeting valuable in the first place. Meta's own response, folding automated targeting and creative optimization into its Advantage+ product line, is a bet that enough first-party signal survives inside its walls to keep performing even as the open web's signal degrades.
Measurement is the quieter casualty. Attribution — knowing which ad actually caused which purchase — was already imprecise, and removing individual-level tracking makes it harder to prove a specific campaign, rather than general brand presence or seasonal demand, drove a specific outcome. Marketers are adjusting to reporting that describes aggregate lift rather than a traceable path from impression to purchase.
The likely endpoint is not less advertising but differently targeted advertising, concentrated more heavily around platforms with a direct, consented user relationship and less available to the open, unauthenticated web that cookies used to stitch together. Whichever way Chrome's cookie policy ultimately lands, the industry has already spent two years rebuilding around the assumption that individual tracking is going away — and that rebuild is not one Google's own hesitation can undo.