In order to decide what ad to show to a person, Facebook and Twitter have sometimes drawn on data about other apps that are already installed on that person’s phone. If that person has downloaded a lot of games, including ones that cost money, they may be shown an ad for a paid game that they don’t already have.

But now Apple is quietly moving to prevent app developers from accessing that app-download data for ad targeting purposes as part of its attempt to appear more privacy-friendly.