Ad Tech Briefing: Farewell to Google’s Privacy Sandbox, we barely knew ye

However, last week, Google confirmed that it was retiring the project, ending half a decade of efforts, which often involved much chagrin.

After debuting in late 2019, Privacy Sandbox involved many rewrites, delays and (ultimately) dwindling faith. It now lies in the Google graveyard, with its obituary lying beside that of Google Glass, Google+; no doubt Privacy Sandbox merch will be looked upon with the same sense of nostalgia as DoubleClick-branded kit years from now.

The birth & promise

At the start of the decade, even before the Covid-19 pandemic, Google introduced Privacy Sandbox with significant fanfare and an unmistakably ambitious premise: to replace third-party cookies in its Chrome browser with a suite of browser-native APIs that would protect user privacy while still enabling ad targeting, measurement and fraud prevention. 

The initiative promised five APIs for things like conversion measurement, “trust tokens,” interest grouping via cohorts — all built into the browser itself. The industry watched keenly, hopeful that this might be a credible way to reconcile publisher ad revenues with user privacy.

The hurdles & slow burn

From the start, however, the sand under the Sandbox was loose. The ad-tech ecosystem questioned whether Google would give itself an advantage; whether the proposed APIs would offer the utility and performance advertisers expected; and whether the sheer complexity of the browser-based model could match the decades of investment behind cookies. Over successive years, the project suffered delays — targeted deprecation dates for cookies kept slipping — and the momentum began to wane.

However, in March 2025, publishers told Digiday that investment in the initiative had stalled and publishers and adtech vendors were pulling back, and by May 2025 — after Google confirmed that it was to U-turn on its plans got third-party cookies in Chrome — publishers bluntly declared: “It’s dead..”

Regulatory pressure

The crisis came not simply from internal decay, but from external pressure. Regulatory scrutiny piled up, with the U.K.’s Competition and Markets Authority questioning whether the Sandbox commitments were still necessary or whether Google’s dominance in Chrome and ad tech had been baked into the design.

Then in April, Google publicly announced it would step back from fully disabling third-party cookies by default in Chrome — a deferral that many interpreted as the practical death knell for the Sandbox as originally conceived.

The aftermath and what stayed

What remains of Privacy Sandbox now is a set of half-built APIs, some browser privacy features, and a cautionary tale. Many publishers and ad-tech firms moved on, focusing instead on first-party data and alternate identity strategies.

Digiday found that adoption of Sandbox tests had effectively ended for some: “I don’t know why anyone would [focus on Privacy Sandbox] again,” one consultant told the publication. Google still insisted that the APIs are alive even after this sentiment became popular. But the bright vision of replacing the cookie with a clean, open-standard browser-based stack now seems to have faded.

The legacy

So what do we remember? The Privacy Sandbox will be studied for lessons. 

• The scale of re-engineering ad tech that browsers and ecosystems face when shifting away from cookies.
• The tension between privacy goals and ad-tech utility — “you make something more private, it becomes less addressable and less measurable,” one publisher told Digiday.
• The power of regulation and competitive forces to up-end even the biggest projects of tech giants.
• And perhaps that no matter how well-intentioned an initiative may be, without market alignment, incentives and clear timelines, it can wither.

In memoriam

Here lies the Google Privacy Sandbox — launched with idealism, delayed by complexity, hobbled by regulatory scrutiny, and ultimately paused by its own parent’s strategic retreat. The ad tech world moves on, but the memory remains: the sandbox, once brimming with possibilities, stands empty now.

May its story guide the next generation of digital ad innovation — modest, realistic, and built for the real world, not just the browser’s ideal.

What we’ve heard

“I can’t believe they gave them the stage to announce a fork in the [Transaction ID] project.” 

– One attendee of the 2025 Prebid Summit expressed surprise that The Trade Desk CEO was given the stage to discuss OpenAds, a development many saw as a rebuke to its efforts, and launch of a sell-side product. 

Numbers to know

• 4.3%: The global annual inflation rate for the ad industry this year, per World Federation of Advertisers research.
• 4.2%: The projected annual inflation rate for the ad industry in 2026, according to the WFA. 
• 3.8%: The annual inflation rate for the U.S. ad industry this year, per the WFA.
• 4.0%: The projected annual inflation rate for the U.S. ad industry in 2026, according to the WFA.   

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