appId property

A string that uniquely identifies a mobile application from which the data was collected to the Google Ads API.

For iOS, the ID string is the 9 digit string that appears at the end of an App Store URL (for example, "422689480" for "Gmail" whose App Store link is https://apps.apple.com/us/app/gmail-email-by-google/id422689480). For Android, the ID string is the application's package name (for example, "com.google.android.gm" for "Gmail" given Google Play link https://play.google.com/store/apps/details?id=com.google.android.gm) This field should not be empty when creating a new third party app analytics link. It is unable to be modified after the creation of the link.

Immutable.