Privacy Policy
Last updated: July 2026
Welcome to Stress (the “App”). We understand how important your personal information is and will strictly comply with applicable laws and take appropriate security measures to protect it. This Privacy Policy explains how we collect, use, store, and protect your information. Core commitment: Health data read by the App is used only on your device to calculate stress and related insights. It is not uploaded to our servers and is not used for advertising or marketing.
1. Information We Collect
The App is a health monitoring tool based on Apple HealthKit. With your permission, we read health data directly related to stress monitoring on your device for on-device calculation. This data is not sent to our servers. 1. Health data (via Apple HealthKit authorization; on-device only) • Heart rate variability (HRV): used to calculate stress levels • Resting heart rate (RHR): an auxiliary indicator for stress assessment • Heart rate data: used for stress monitoring in Realtime mode • Sleep data: used to improve your personal baseline model • Workout data: used to pause stress monitoring during workouts for accuracy • Date of birth: used to personalize workout heart-rate zones by age All of the above health data is read and calculated only on your device. It is not uploaded to our servers and is not written to any cloud database we control. 2. Device and settings data (non-health content) • App preference settings (such as monitoring mode, notification preferences, card layout) • Optional sync of settings across your devices via iCloud Key-Value Storage (settings only) • Device identifiers used for local data deduplication 3. Information we explicitly do not collect We do not request or actively collect: • Your name, email, phone number, government ID, or other identity information • Your location, contacts, or photo library • Your browsing or search history • Any data used for ad profiling, targeted marketing, or third-party advertising • Any cloud profile that would require creating an account Because we do not offer accounts and do not sync health data to the cloud, such information is neither needed nor collected or uploaded.
2. How We Use Your Information
Your health data is used only on your device for the following purposes: 1. Stress level calculation: Compare your HRV and heart-rate data with your personal baseline using a Z-Score algorithm to produce four stress levels (Full of Energy / Feeling Good / A Bit Worn Out / Running on Empty) 2. Personal baseline: Build your personalized physiological model from about the past 30 days of health data 3. Trend analysis: Show how your stress changes over time to help you understand your state 4. Breathing exercises: Suggest suitable breathing practices based on your current stress state Our commitments: • On-device only: Stress scores, baselines, and trends are computed locally and do not rely on our servers • No server upload: We do not upload HealthKit health data or stress results to our servers • We do not use your health data for advertising or commercial marketing • We do not sell, rent, or otherwise provide your health data to any third party • We do not store HealthKit data in iCloud or any remote server
3. Storage and Security
1. Local storage • Health-related results (stress records, baseline data) are encrypted and stored locally with Apple SwiftData • App settings are stored locally with UserDefaults • Raw health samples remain in the system Health app, managed by Apple HealthKit 2. iCloud sync (optional) • Syncs only app preference settings (such as card layout and monitoring mode); does not sync any health data • Uses Apple NSUbiquitousKeyValueStore (iCloud Key-Value Storage) • You can turn off iCloud sync anytime in system settings 3. Apple Watch sync • Baseline parameters are transferred between iPhone and Apple Watch via WatchConnectivity • Transfers include statistical parameters (mean, standard deviation) only—not raw health records • Sync happens between your own devices and does not go through our servers 4. Data security • All health data and stress results stay on your devices and do not pass through any third-party servers we operate • The App does not include third-party analytics SDKs or tracking frameworks • The App does not transmit any health data over the network
4. Your Rights
1. Access: You can view stored stress records and baseline data in the App at any time 2. Deletion: You can delete data by: • Revoking the App’s HealthKit access in the Apple Health app • Uninstalling the App, which deletes all locally stored data 3. Portability: You can export health data through the Apple Health app 4. Withdraw consent: Manage the App’s data access anytime in iPhone Settings > Privacy & Security > Health 5. Turn off iCloud sync: In iPhone Settings > Apple ID > iCloud, turn off iCloud for this App
5. Children’s Privacy
The App is primarily intended for adults. We do not knowingly collect personal information from children under 13. If you are under 13, please use the App with a parent or guardian and have them help complete HealthKit authorization. If we learn that we have inadvertently collected a child’s personal information, we will delete it as soon as reasonably possible.
6. Updates to This Policy
We may revise this Privacy Policy as laws or our practices change. Updated policies will be published in the App with an update date. For material changes, we will provide a clear in-app notice. Please review this policy regularly to understand how we protect your information.
Contact Us
If you have questions or suggestions about this Privacy Policy, please contact us via Settings → Feedback in the App.