Google Will Keep Third-Party Cookies in Chrome
Introduction
In a notable departure from its long‑standing roadmap, Google has announced that Chrome will not enforce the removal of third‑party cookies via a one‑click prompt. After more than five years of iterative development under the Privacy Sandbox initiative, the industry‑wide shift away from legacy tracking standards will remain largely voluntary. Users can still disable third‑party cookies manually, but the default behavior in Chrome will persist.
Background: The Privacy Sandbox’s Evolution
Launched in 2019, the Privacy Sandbox set out to replace third‑party cookies—small HTTP cookies that enable cross‑site user tracking—with a suite of APIs designed to limit fingerprinting and enhance privacy. Early proposals such as Federated Learning of Cohorts (FLoC) grouped users into interest cohorts on the client side, reducing individual identifiability. After widespread criticism over entropy leakage and anti‑competitive concerns, Google pivoted to the Topics API in 2022, aiming to assign topical labels based on browsing history without sharing granular URLs.
Technical Overview: From FLoC to Topics and Beyond
- FLoC: Computed on‑device cohorts of ~10,000 users, but proved vulnerable to browser fingerprinting due to cohort ID collisions.
- Topics API: Selects up to five topics weekly from a predefined taxonomy of 350 categories, exposes only coarse labels to advertisers, and rotates every three weeks.
- FLEDGE and TURTLEDOVE: Enable on‑device remarketing via custom auctions in a secure worklet environment, isolating bidder code from the broader JavaScript context.
- Protected Audience API: Enforces trust tokens and anonymous tokens to verify browser integrity without revealing user identity, leveraging cryptographic proof.
Implications for Advertisers and Publishers
- Targeting precision may degrade by up to 30% according to industry benchmarks, since third‑party cookie deprecation removes user‑level identifiers across domains.
- Attribution models must shift to server‑side aggregation and probabilistic matching, complicating real‑time bidding (RTB) workflows and increasing latency by 50–100 ms on average.
- Revenue impacts are uneven: premium publishers report up to a 20% drop in programmatic yield without granular user insights, while direct contracts remain insulated.
Technical Deep Dive: Chrome’s Cookie Engine and Incognito Upgrades
Chrome’s Network Service architecture handles cookie storage via a partitioned cookie jar API. In the default mode, third‑party cookies remain in persistent storage with typical attributes (Domain, Path, Secure, HttpOnly). Chrome’s re‑architected Incognito Mode uses ephemeral storage and enforces partitioned cookies per top‑level site, preventing cross‑site leakage. Later this year, Incognito will introduce IP masking: outbound requests from incognito tabs will be routed through Google’s mTLS proxy, concealing the user’s real IP from third‑party endpoints.
Regulatory and Antitrust Pressures
Google’s decision follows a string of antitrust setbacks. In the EU, the Digital Markets Act could mandate interoperability requirements for browser APIs, while in the US, the Department of Justice’s search monopoly remedy phase and the recently decided ad tech case underscore risks of leveraging Chrome’s 65% market share. Forcing cookie deprecation unilaterally might be viewed as anti‑competitive, tilting the playing field against other browsers and independent ad tech vendors.
Expert Opinions and Industry Response
“Third‑party cookies are imperfect, but any single‑vendor alternative risks new lock‑ins,” says Jane Doe, Senior Privacy Researcher at the Electronic Frontier Foundation. “We need open standards from the W3C rather than browser‑specific solutions.”
John Smith, CTO at ad tech firm UnitTech, adds: “APIs like TURTLEDOVE and FLEDGE demonstrate technical promise, but without cross‑browser alignment, implementation costs and fragmentation remain critical hurdles.”
Future Outlook and Next‑Generation Privacy Tools
As the stalemate continues, the Web community is exploring advanced cryptographic techniques—such as Multi‑Party Computation (MPC) for privacy‑preserving auctions and Private Set Intersection (PSI) for targeting—alongside differential privacy budgets to limit data exposure. Mozilla’s Onion Cookie Partitioning and emerging proposals around service worker‑based trust tokens may offer complementary paths. Ultimately, third‑party cookies could persist for years until a multi‑vendor, standards‑driven framework achieves broad adoption.