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Protected Audience API (FLEDGE) ceased operations on October 17, 2025

Protected Audience API (FLEDGE)

Privacy-Preserving Advertising TechnologyProduct· part of Google

Enabled interest-based remarketing and on-device ad auctions without exposing user browsing data to advertisers or ad networks, preserving user privacy while maintaining advertiser targeting capabilities.

Last updated Sep 26, 2026 by ATDb automated enrichment · Connections updated Sep 28, 2026

Founded
2019
HQ
Mountain View, California, United States
Parent
Google
Connections
9

AI-drafted from public sources3 sources cited

At a glance

8integrations1corporate family
Privacy-First AdvertisingProgrammatic Platform

About

Google-developed browser API positioned as the primary cookie-alternative for remarketing within the Chrome Privacy Sandbox initiative

The Protected Audience API, originally proposed as FLEDGE (First Locally-Executed Decision over Groups Experiment) in 2019, was Google's flagship Privacy Sandbox proposal designed to enable interest-based advertising and remarketing without third-party cookies or cross-site tracking. Built into the Chrome browser, it allowed advertisers to define audience groups ('interest groups') that were stored on-device, with ad auctions executed locally within the browser using JavaScript worklets — ensuring that user browsing history never left the device. This represented a fundamental architectural shift from server-side programmatic advertising toward browser-mediated, privacy-preserving ad decisioning. The API was a central pillar of Google's broader Privacy Sandbox initiative, which aimed to replace the functionality of third-party cookies with a suite of purpose-built, privacy-respecting APIs. After years of development, industry consultation, and trials involving major DSPs, SSPs, and advertisers, the Protected Audience API reached general availability in Chrome in 2023. It attracted significant industry attention and investment from AdTech players including Google's own Display & Video 360, as well as independent platforms like The Trade Desk, Criteo, and various SSPs that built integrations and conducted live testing. Despite substantial technical progress and ecosystem adoption efforts, Google announced in July 2024 that it would no longer deprecate third-party cookies in Chrome, fundamentally undermining the urgency of the Privacy Sandbox APIs. Following this reversal, the Protected Audience API was officially retired on October 17, 2025. Its legacy lies in advancing industry thinking around on-device computation, auction design, and privacy-preserving advertising architecture — concepts that continue to influence browser-based and edge-computing approaches to AdTech.

Business model

Open Web Standard / Browser API

Target market

Enterprise

What they offer

  • Protected Audience API (FLEDGE)

    On-device ad auction framework allowing browsers to store interest group memberships and run JavaScript-based auctions locally without server-side user data exposure

  • Interest Group API

    Mechanism for advertisers to add users to interest groups stored within the Chrome browser for later targeting

  • On-Device Auction Worklets

    Sandboxed JavaScript execution environments within Chrome that ran bidding and scoring logic during ad auctions without network data leakage

  • Trusted Execution Environments (TEE) Integration

    Server-side trusted execution environment support for key-value lookups during auctions while preserving privacy guarantees

  • Fenced Frames Integration

    Privacy-preserving ad rendering mechanism designed to display winning auction creatives without leaking auction data to the embedding page

Key features

On-device interest group storage within Chrome browserBrowser-mediated ad auctions using JavaScript workletsNo cross-site user data transmission to advertisersSupport for multiple seller and buyer auction configurationsIntegration with Trusted Execution Environments for real-time signalsCompatible with existing DSP and SSP auction logic via JavaScriptFenced Frames support for privacy-safe ad renderingReporting APIs for aggregate and event-level auction outcomes

Use cases

Remarketing to users who previously visited an advertiser's websiteInterest-based audience targeting without third-party cookiesPrivacy-preserving programmatic display advertisingOn-device real-time bidding for browser-based inventoryCross-publisher frequency capping without cross-site tracking

Customer segments

Demand-Side Platforms (DSPs)Supply-Side Platforms (SSPs)Advertisers and brands running remarketing campaignsAd measurement and verification vendorsPublishers monetizing Chrome-based inventory

Tech & specs

Technology stack

Chromium browser engineJavaScript worklets (sandboxed execution)Trusted Execution Environments (AWS Nitro, Google Cloud TEE)Web APIs (navigator.joinAdInterestGroup, runAdAuction)Fenced FramesPrivate Aggregation APIKey-Value server infrastructure

Security & compliance

GDPR-aligned designUK CMA Privacy Sandbox commitmentsW3C WICG standards processPrivacy-by-design architecture

Deployment

Browser-native (Chrome)

API

No

Explore further

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