Google Says Its Ads Won't Use Alternative Identifiers

What Changed

A year after Chrome announced its plan to phase out third-party cookies, much of the ad industry was preparing a replacement: alternative IDs built from people's email addresses. On March 3, 2021, Google said its own ad products wouldn't take part.

In a post on Google's blog, David Temkin, Google's director of product management for ads privacy and trust, wrote that once third-party cookies were gone, Google would not build alternate identifiers to track individuals as they browse across the web, nor use them in its products. Its web ad products would instead be powered by privacy-preserving APIs that prevent individual tracking, the Privacy Sandbox technologies Chrome was building.¹ The first of these was FLoC: Google said it expected to begin testing FLoC-based audiences with advertisers in Google Ads in the second quarter of 2021.¹ FLoC was later replaced by the Topics API.

Google drew a line between tracking and first-party relationships. It said it would continue to support first-party relationships on its ad platforms, so advertisers could still use data their own customers had given them. The commitment also covered the web only: the post didn't discuss mobile apps.¹

Why It Mattered

For advertisers, it settled a practical question: an email-based ID bought from a third party would not help them target or measure on Google's ad network once cookies were gone. Inside Google's products, the options were the Privacy Sandbox and their own customer data.

It also split the market. Alternative IDs such as The Trade Desk's Unified ID 2.0 would work across the open web outside Google, while Google's demand stayed on Google's own technology. Critics argued that Google was using privacy to strengthen its market position, the concern the UK's competition regulator was already investigating.²

Google hardened its position two months later. Jerry Dischler, its head of ads, said third-party cookies and the identifiers some in the industry were advocating "simply cannot be trusted in the long term". AdExchanger reported that LiveRamp had confirmed with Google that buyers could still use its ID on supply-side platforms, but only in private marketplace deals.³

The pledge was about building identifiers, and Google later loosened a related rule: in February 2025 it lifted its ban on fingerprinting in its ad platforms.