privacy-in-practice

Wearables and Period Data: Apple Watch, Fitbit, Garmin

Apple Watch, Fitbit, and Garmin all track cycle data. Where that data goes, who can access it, and how their privacy models compare.

Three Platforms, Three Privacy Models Fitness trackers have added cycle tracking features as reproductive health monitoring has become more common. Apple Watch, Fitbit, and Garmin cover the majority of the wearable market, and each has a meaningfully different approach to where cycle data lives and who can access it. This is not a comparison of cycle tracking features. It is a comparison of what each platform does with the data those features generate. Apple Watch and Apple Health Apple's cycle tracking is built into the Health app on iPhone, with Apple Watch passively contributing biometric data (heart rate variability, skin temperature on Apple Watch Series 8 and later, respiratory rate) that Apple's algorithm uses to estimate cycle phases. Where the data lives. Health data is stored locally on your iPhone in HealthKit. If you enable iCloud backup, health data is included. Apple's documentation states that iCloud Health data is encrypted end to end, meaning Apple cannot decrypt it. Only your trusted devices can. This is different from most other iCloud data, which Apple can read. The third party app problem. The weak point in Apple Health's privacy model is permissions. Third par