What is Mobile Ad ID?
A resettable identifier assigned by mobile operating systems that enables cross-app tracking for targeted advertising.
Also known as: IDFA, GAID
The Mobile Ad ID (IDFA on iOS, GAID on Android) is the primary mechanism advertisers use to track you across apps.
How It Enables Tracking
- Every app on your phone can read the same Ad ID
- Apps send the Ad ID to their analytics and ad SDKs
- Data brokers collect Ad IDs from thousands of apps
- They combine the data to build a comprehensive profile: apps used, places visited, purchases made
- Advertisers buy access to target specific profiles
The $200 Billion Industry
Mobile advertising revenue depends on this tracking. When Apple introduced App Tracking Transparency (ATT) in iOS 14.5, requiring opt-in consent, Facebook estimated it would lose $10 billion in annual revenue.
How to Disable
- iOS: Settings > Privacy > Tracking > Turn off "Allow Apps to Request to Track"
- Android 12+: Settings > Privacy > Ads > Delete advertising ID
Disabling the Ad ID significantly reduces cross-app tracking but doesn't eliminate it entirely.
Related Terms
Advertising ID
A unique identifier assigned to your mobile device by the operating system, used by apps and advertisers to track your behavior across applications.
Browser Fingerprinting
A tracking technique that collects information about your browser, device, and settings to create a unique identifier. Unlike cookies, fingerprints are nearly impossible to delete and can track you across websites without your knowledge or consent.
Third-Party Tracking
The practice of monitoring user behavior across multiple websites using embedded scripts, pixels, cookies, and fingerprinting techniques.
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