Hi,
I’m currently working on an app that utilizes sleep data from HealthKit to provide users with meaningful insights about their sleep.
To ensure a smooth user experience, I’d like to understand when sleep data collected by the Apple Watch is saved to the HealthKit store and when it gets synced to the iPhone.
Ideally, I want to fetch sleep data right after the user wakes up and opens our app. However, to do this reliably, I need to know the timing of how and when this data becomes available in the iPhone’s HealthKit store.
I’ve looked through the official documentation and relevant WWDC sessions but couldn’t find clear information on this topic.
If anyone has insights or experience with how and when the Apple Watch syncs HealthKit data—especially sleep records—to the iPhone, I’d greatly appreciate your input.
Thanks!
The HealthKit store synchronization timing between watchOS and iOS is determined by the system, and there is currently no public documentation in that regard.
In your case, you can consider using HKObserverQuery + enableBackgroundDelivery(for:frequency:withCompletion:) to observe the changes on the sleep samples. If the sleep samples in the iOS HealthKit store change, your app will be woken up (if it is suspended), and the updateHandler of the query will be called. You can then fetch the data from there.
Best,
——
Ziqiao Chen
Worldwide Developer Relations.