A mobile advertising ID (MAID) is the generic name for the resettable, device-level advertising identifier issued by a mobile operating system. The two that matter in practice are Apple’s IDFA (Identifier for Advertisers) and Google’s AAID (Android Advertising ID), sometimes written simply as AdID.
Why a separate identifier exists
Before MAIDs, advertisers used hardware identifiers that users could neither see nor change. MAIDs were introduced to give the same commercial function within limits the user controls: the ID can be reset, which severs the history attached to it, or disabled altogether.
How MAIDs are used in location data
In a location dataset, the MAID is usually the key that ties a series of observations into a single device trajectory. That is what makes measurement possible — establishing that the same device saw an advert and later visited a store is the basis of visit attribution. It is also why MAID availability and consent status materially affect the quality of any location panel.
Availability has fallen
Apple’s App Tracking Transparency prompt, introduced with iOS 14.5, made the IDFA opt-in. Opt-in rates vary widely by app category, so an iOS-heavy panel will contain far fewer usable identifiers than an Android one. Any vendor quoting panel size should be asked how that figure splits by platform.
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