The Ad Response ID is the value in the responseIdentifier field, which is the unique identifier of an ad response. The responseIdentifier field is available for an ad or a mediation response.
The Ad Response ID can be used to identify and block an ad in the Ad review center in Ad Manager and AdMob.
Ad Response IDs are available to review in the Ad review center for 30 days.
Learn more about how to retrieve the Ad Response ID on the Google Developers site for Android and iOS.