Apple’s crusade to tighten privacy in its App Store is shifting into another gear. The company is cracking down on developers who use a technique called device fingerprinting to track user activity – even if they’ve opted out.

Specifically, the company wants devs to explain why they’re using certain application programming interfaces (APIs) and third-party software development kits (SDKs) in their apps. As part of its app store review process, it is also requiring developers to update their privacy documentation.

Those who fail to comply could find their apps denied approval in the App Store.