Privacy Notice
Last updated: 2 November 2026
In short
- Hydra stores your profile, estimates and history locally on your devices — there is no developer-operated server or cloud database.
- Health data stays in Apple Health; Hydra only reads what you permit and writes dietary water only for drinks you explicitly log.
- The one exception to “data stays on device” is the optional WeatherKit request, which sends approximate location to Apple’s weather service.
- No accounts, no ads, no third-party analytics or crash-reporting SDKs in the current build.
What Hydra accesses and why
Hydra requests HealthKit access for the data types listed below. Every permission is optional — if you decline, a baseline estimate calculated from your profile preferences alone remains available.
| Data type | Purpose |
|---|---|
| Heart rate | Informs exertion-based hydration adjustments |
| Active energy | Accounts for calories burned during the day |
| Workouts | Duration and type of workouts factor into the estimate |
| Body mass | Used as a baseline variable in the hydration formula |
| Dietary water | Read to reflect recorded intake; written only for drinks you explicitly log or correct |
| Age | Age-related adjustment to the estimate |
| Biological sex | Physiological adjustment to the estimate |
Hydra writes dietary-water data to Apple Health only for drinks you explicitly log or correct. It does not write any other data type.
Optional local weather
When you enable local weather and grant location permission, Hydra requests your approximate location to call Apple WeatherKit for the current local temperature. This is the one case where data leaves your device. If weather or location is unavailable or denied, Hydra falls back to the climate preference you set in the app.
Where your data is stored
Hydra has no developer-operated backend and no CloudKit service. Your profile, estimates and history are stored locally by the app on your devices. Health information is accessed through Apple Health / HealthKit. Explicitly logged water may also be written to Apple Health.
The one exception is the optional WeatherKit request described above, which sends approximate location to Apple’s weather service to fetch local weather.
Apple Health and HealthKit
Hydra keeps its own estimates and profile in the app. Health data accessed through HealthKit is read at the time of estimation and is not separately duplicated or stored by Hydra outside the app’s working memory.
You can change or revoke Health permissions at any time in iOS Settings → Health → Data Access & Devices, or directly in the Health app. Declining Health access still leaves a baseline estimate available.
What Hydra does not do
- No accounts — Hydra does not require sign-up or login.
- No ads — the app contains no advertising.
- No third-party analytics or crash-reporting SDKs in the current build.
- No selling, sharing or monetising of your data.
Retention and deletion
Because data lives in the app on your devices, deleting the app removes its local data from that device. Drinks written to Apple Health remain in Apple Health until you delete them there.
Children
Hydra is a general-wellness app and is not designed for or directed at children under 13. It does not knowingly collect personal information from children.
Changes to this notice
If this notice is updated, the revised version will be posted here with an updated date. Continued use of the app after a revision constitutes acceptance of the updated notice.
Contact
Questions or concerns about this notice? Contact the developer at [email protected].
For owner review — not part of the published notice
- Retention / backups: Confirm the exact retention and deletion behaviour — does any data persist in device backups (iCloud backup, encrypted iTunes/Finder backup)?
- Notifications / reminders: The current build has no reminder feature. If reminders are added later, this notice will need updating.
- Legal entity name: Confirm the legal entity to display as the developer (currently shown as “3D Freedom”).
- App Store privacy labels: Verify that the App Store privacy nutrition labels match the statements in this notice before submission.
- Effective date: Confirm the date this notice should go live (currently set to 2 November 2026).