When Google first announced Privacy Sandbox in 2019, we dismissed it as vaporware. Five years and countless delays later, it's actually launching—and it's transforming how digital advertising works. The industry spent years preparing for a world without cookies. Now we're finally building it.
What Is Privacy Sandbox?
Privacy Sandbox is Google's collection of APIs designed to enable advertising use cases without cross-site tracking. Instead of tracking individuals, it uses aggregated, on-device processing to maintain privacy while allowing targeting and measurement.
Key APIs for Advertisers
- Topics API: Interest-based targeting without tracking
- Protected Audiences: Retargeting and custom audiences
- Attribution Reporting: Conversion measurement
- Private Aggregation: Aggregate reporting
Topics API Deep Dive
Topics replaces interest-based targeting. The browser observes your browsing, assigns topics, and shares a random subset with advertisers.
How Topics Works
- Browser classifies sites into ~470 topics
- Weekly, top 5 topics calculated per user
- One random topic selected from each of last 3 weeks
- 5% noise added (random topic instead)
- Advertiser receives 0-3 topics per user
Topics Limitations
You can only see topics from sites where your ad tech was present. New advertisers may see very few topics initially. The taxonomy is broad—"Sports" not "Fantasy Football."
Protected Audiences (FLEDGE)
Enables retargeting without cookies. Interest groups live in the browser, auctions happen on-device.
The New Auction Flow
- User visits site, gets added to interest group
- Interest group stored locally in browser
- On ad request, on-device auction runs
- Winning ad rendered in fenced frame
- Limited reporting back to servers
Latency Concerns
On-device auctions add latency. Early tests show 50-200ms additional time. Publishers watching viewability and UX impacts closely.
Attribution Reporting API
Conversion measurement without user-level tracking. Two reporting modes:
Event-Level Reports
- Limited data (3 bits for clicks, 1 for views)
- Delayed by hours to days
- Good for optimization signals
Summary Reports
- Aggregate data with noise
- Rich conversion data possible
- Requires aggregation service
What This Means for Mobile
Privacy Sandbox on Android mirrors web APIs:
- Topics API for Android apps
- Protected Audiences for app retargeting
- Attribution Reporting for in-app conversions
- SDK Runtime for privacy boundaries
Preparing for the Transition
- Test now: Origin trials available in Chrome
- Invest in first-party data: Still the gold standard
- Update measurement: New APIs require new infrastructure
- Diversify targeting: Don't rely solely on Privacy Sandbox
Stay Ahead of Privacy Changes
ClicksFlyer is building Privacy Sandbox integrations to ensure seamless measurement as the industry transitions. Let us handle the complexity.