The End of Third-Party Identifiers Is Coming to Mobile
For years, mobile ad targeting has relied heavily on device-level identifiers like Google's Advertising ID (GAID). But with growing privacy regulations and user expectations, Google is building a new privacy-first framework: the Privacy Sandbox on Android. This initiative mirrors the Privacy Sandbox already under development for Chrome and aims to provide effective advertising without compromising user privacy.
For mobile game developers and app publishers who depend on ad revenue, these changes are not optional — they will fundamentally alter how ads are targeted, measured, and attributed across the Android ecosystem. Understanding the Privacy Sandbox now is critical to protecting your revenue streams.
What Is the Privacy Sandbox on Android?
The Privacy Sandbox on Android is a set of APIs and system-level technologies designed to replace traditional cross-app tracking with privacy-preserving alternatives. Instead of sharing raw user data with ad networks, the Privacy Sandbox processes interest signals, attribution data, and audience information on-device, limiting the data that leaves the user's phone.
Google has stated that the GAID will eventually be phased out, and the Privacy Sandbox APIs will become the primary mechanism for ad personalization and measurement on Android. The project entered general availability in early 2025, and adoption milestones continue through 2026 and beyond.
Key Design Principles
- On-device processing: Interest and audience signals are computed locally, not on remote servers.
- Data minimization: Only aggregated or anonymized data is shared with ad tech providers.
- User control: Users can manage their ad privacy settings directly in Android system settings.
- Backward compatibility: Google is providing a migration period where both GAID and Privacy Sandbox APIs coexist.
The Three Core APIs Publishers Must Understand
1. Topics API
The Topics API replaces the concept of cross-app interest tracking. Instead of ad networks building behavioral profiles by following users across apps, the Topics API assigns a small set of interest categories (called “topics”) to each user based on recent app usage. These topics are determined on-device, refreshed weekly, and limited in granularity to prevent re-identification.
For publishers, the Topics API means that buyer demand will shift. Advertisers who previously relied on granular audience segments will now work with broader interest categories. This may impact eCPMs for niche audiences but could improve fill rates for apps in popular categories like gaming, entertainment, and utilities.
2. Attribution Reporting API
The Attribution Reporting API provides a privacy-safe way to measure ad conversions — for instance, whether a user who saw an ad in your game later installed the advertised app. It supports both event-level reports (limited data, suitable for optimization) and aggregate reports (noisy but richer data, suitable for campaign analysis).
This API is critical for maintaining advertiser confidence. If advertisers cannot measure the effectiveness of campaigns running in your app, they will reduce bids or shift budgets elsewhere. Publishers should ensure their mediation partners and SDKs support this API to preserve campaign performance data.
3. Protected Audiences API (formerly FLEDGE)
The Protected Audiences API enables remarketing and custom audience targeting without revealing which audiences a user belongs to. Audience membership is stored on-device, and ad auctions involving these audiences run locally rather than on ad servers. This means ad networks can still serve relevant ads to high-value user segments, but without the privacy risks of server-side audience sharing.
For publishers monetizing through programmatic demand, the Protected Audiences API preserves the ability of demand-side platforms to bid on valuable users. However, the on-device auction model introduces new latency considerations that publishers and their ad mediation stacks must account for.
Impact on eCPMs and Fill Rates
The transition to Privacy Sandbox will not affect all publishers equally. Here is what you should expect:
- Short-term eCPM pressure: During the transition period, some advertisers will be slow to adopt the new APIs, leading to reduced bid density and potential eCPM declines of 10-20% for segments that relied on GAID-based targeting.
- Fill rate stability: Because contextual signals (app category, content type, geo) remain available, fill rates are expected to hold steady for most publishers. Mediation platforms will continue to optimize across demand sources.
- Long-term recovery: As advertisers adopt Topics and Protected Audiences, buyer competition will normalize. Publishers with strong first-party signals (in-app engagement data, user preferences) will be better positioned to command premium eCPMs.
- Gaming advantage: Mobile games tend to have high session times and clear content categories, making them strong candidates for Topics-based targeting. Gaming publishers may see less eCPM disruption than other verticals.
What Publishers Should Do Now
Preparation is key. The publishers who act early will have a competitive advantage when the GAID is fully deprecated. Here are the steps you should take:
- Audit your SDK stack: Confirm that your ad mediation platform and all demand partner SDKs support Privacy Sandbox APIs. Major players like Google Ad Manager, AdMob, and most large SSPs have already integrated support.
- Test in sandbox mode: Use the Privacy Sandbox developer preview to test how your ad performance changes when GAID is unavailable. Google provides testing tools and emulators for this purpose.
- Strengthen first-party data: Build in-app engagement signals that do not depend on cross-app tracking. Metrics like session duration, levels completed, items purchased, and content preferences can enhance contextual targeting.
- Evaluate your waterfall: Review your ad waterfall configuration. Networks that are slow to adopt Privacy Sandbox may underperform. Consider adjusting priority or floor prices during the transition.
- Monitor industry benchmarks: Join industry groups and follow Google's developer documentation for updates on API changes, deprecation timelines, and best practices from other publishers.
Timeline and Milestones
Google has been rolling out Privacy Sandbox on Android in stages. Here are the key dates publishers should track:
- 2023: Developer preview and beta launch of core APIs.
- 2024: Privacy Sandbox APIs reach general availability on Android 13+ devices. Limited production testing begins.
- 2025: Broader production rollout. Major ad networks integrate Privacy Sandbox support into their SDKs. Google begins signaling GAID deprecation timelines.
- 2026: GAID deprecation expected to begin for a percentage of Android users. Publishers without Privacy Sandbox support will experience measurable revenue impact.
- 2027 and beyond: Full GAID deprecation anticipated. Privacy Sandbox becomes the sole framework for ad personalization on Android.
Key takeaway: The shift to Privacy Sandbox is not a distant future event — it is happening now. Publishers who wait until GAID is fully deprecated will face revenue disruption. The time to prepare is today.
Final Thoughts
Privacy Sandbox on Android represents the most significant structural change to mobile ad targeting since the introduction of app tracking transparency on iOS. For mobile game developers and app publishers, it is both a challenge and an opportunity. The publishers who invest in understanding the new APIs, testing their ad stacks, and building first-party engagement signals will emerge stronger. Those who ignore these changes risk falling behind as the ecosystem evolves.
Stay informed, test early, and work closely with your ad monetization partners to ensure a smooth transition. The future of mobile advertising is privacy-first — and the transition is already underway.