Device ID

A device ID is a a type of unique, anonymized string of numbers and letters associated with a single, specific mobile device or user.

What is a Device ID?

Stored directly on the mobile device itself, device IDs have up until recently, been used by advertisers, marketers, and other third parties to understand actions taken by users including:

  • Pre-install engagement such as ad clicks or impressions
  • In-app events including purchases and leveling up

While device IDs have previously played an instrumental role in all stages of the user journey and experience, including install attribution, in-app personalization, audience segmentation, and overall app performance, the industry saw a shift with the rise of Apple’s App Tracking Transparency (ATT) prompt and is now favoring other, more privacy-centric solutions such as aggregated attribution and predictive analytics.

What types of Device ID exist?

  • Android – Google Advertising ID (GAID)
  • iOS – Identity for Advertisers (IDFA)

Note: From iOS 14 and onward, users are prompted with an ATT message asking them to choose whether or not they’d like Apple to block the sharing of this ID. For more information, check out our collection on iOS 14 and beyond for more information.

Why have Device IDs previously mattered to advertisers?

In the desktop era, the cookie was the staple of digital advertising and measurement.

The problem is that the average “lifespan” of the cookie is no more than three weeks, creating inconsistencies when measuring long-term user journeys.

One clear benefit of the device ID as compared to the cookie was its persistence, or ability to present a clear view of a user based on deterministic data across longer, if not indefinite, stretches of time. Measurement based on device IDs could only be “interrupted” with a manual device ID reset, which was extremely infrequent.   

Both the GAID and IDFA device ID numbers have been used in various mobile attribution methods, giving a detailed user profile to complement and enhance mobile advertising activity, analyze specific user trends, and to further categorize users into cohorts (groups with similar traits). Most importantly, with a device ID, marketers could understand not only identify of their users, but their behavior over time.

This specific use of device ID was known as ID matching, a method of mobile attribution that was considered to be highly reliable and extremely accurate, yet not as privacy-centric as other solutions such as aggregated attribution.

Device ID matching provides a view into user behavior across the user journey. It enables marketers to see whether or not a user viewed or clicked on an ad, installed an app, and even in-app behavior.

While not all publishers enable device ID attribution, or allow marketers to use their platforms for this purpose, device IDs are still one of the clearest and most accurate means of understanding how users move from prospect to customer.

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