After Apple Tightens Tracking Rules, Advertisers Shift Spending Toward Android Devices

Advertisers have begun shifting their spending patterns in the months since Apple Inc. began requiring apps to gain iPhone and iPad users’ permission to track them.

After the tracking change took effect in April, many users of Apple’s iOS operating system have received a high volume of prompts from apps asking permission to track them—requests that most have declined. Less than 33% of iOS users opt in to tracking, according to ad-measurement firm Branch Metrics Inc. Digital advertisers say they have lost much of the granular data that made mobile ads on iOS devices effective and justified their prices.