Apple has allowed app developers to collect data from its one-billion iPhone users for targeted advertising, in an unacknowledged shift that lets companies follow a much looser interpretation of its controversial privacy policy, reports Patrick McGee of the Financial Times.

Months after implementing the iPhone's App Tracking Transparency feature, companies including Snap and Facebook have been allowed to keep sharing user-level signals from iPhones, as long as that data is anonymized and aggregated rather than tied to specific user profiles.

For instance Snap has told investors that it plans to share data from its 306m users — including those who ask Snap "not to track" — so advertisers can gain “a more complete, real-time view” on how ad campaigns are working. Any personally identifiable data will first be obfuscated and aggregated.

Apple has told developers they "may not derive data from a device for the purpose of uniquely identifying it." This means they can observe 'signals' from an iPhone at a group level, enabling ads that can still be tailored to 'cohorts' aligning with certain behavior but not associated with unique IDs.

Apple declined to answer specific questions for this article but described privacy as its North Star, implying it was setting a general destination rather than defining a narrow pathway for developers.

Cory Munchbach, chief operating officer at customer data platform BlueConic, said Apple had to stand back from a strict reading of its rules because the disruption to the mobile ads ecosystem would be too great. There's a lot more to this and you could read it at the Financial Times.