Android Zeroes the Advertising ID for Users Who Opt Out

What Changed

Since 2013, Android users could reset their Advertising ID or opt out of interest-based ads, but apps could still read an ID. Google changed that through Google Play services.

When a user deletes their Advertising ID, apps that try to read it now receive a string of zeros instead of the identifier.¹ The change reached apps running on Android 12 from late 2021, and expanded to apps on all devices that support Google Play from April 1, 2022.^1,2

Google also added a permission. Apps that target Android 13 or later must declare a Google Play services permission, com.google.android.gms.permission.AD_ID, in their manifest to read the Advertising ID at all.¹ Some SDKs, such as Google's own Mobile Ads SDK, declare it automatically. For uses other than ads, such as analytics and fraud prevention, Google points developers to a separate identifier, the App Set ID.¹ It's shared only by apps from the same Google Play developer account on a device, and it resets if none of them uses it for 13 months, so it can't follow a person into other companies' apps.³

Why It Mattered

It brought Android in line with what Apple had done on iOS in 2016: opting out now removes the identifier rather than just setting a flag. Attribution, frequency capping and audience building no longer worked for users who deleted their ID.

The effect was smaller than App Tracking Transparency on iOS, because Android doesn't ask every user. Deleting the ID requires going into settings, so the opt-out depends on people seeking it out, and few do: when Google announced the change in 2021, the attribution company Singular found that about 2% of the 176 million Android phones in its data had turned off ads personalization.⁴

The new permission also made the Advertising ID something apps had to choose to read, rather than something available to any code in the app. It became part of what Google Play reviews when it checks an app's data practices.