Privacy Policy

Last updated: October 2026

Sylph is a privacy-first app. We collect the absolute minimum required to run the app. This policy explains which data is processed when — and which is not.

1. Controller

Martin Rost, c/o flexdienst – #20426, Kurt-Schumacher-Straße 76, 67663 Kaiserslautern, Germany.
Contact: [email protected]

2. General principles

  • Sylph requires no account and no sign-up.
  • We use no tracking pixels, no ad networks, no third-party cookies.
  • Session, history and focus data is stored only on your device (SwiftData).
  • There is no sync via iCloud or our own servers. Between iPhone and Apple Watch, Sylph transfers only purchase status, favorites and haptic setting via Apple’s WatchConnectivity, directly between your devices.

3. Third-party services we use

3.1 RevenueCat (purchase management)

We use RevenueCat, Inc. (USA) to manage the in-app purchase. RevenueCat processes the purchase confirmation of the in-app purchase and the unlock status. Transmitted: an anonymous app-user-ID (UUID), device country, platform and purchase data — no plain identifiers. Legal basis: Art. 6(1)(b) GDPR (contract performance). RevenueCat privacy.

3.2 TelemetryDeck (anonymous analytics)

We use TelemetryDeck (Telemetry GmbH, Germany) for anonymous usage analytics. Personal identifiers are hashed technically; re-identification is not possible. Legal basis: Art. 6(1)(f) GDPR (legitimate interest in product improvement). TelemetryDeck privacy.

3.3 Sentry (crash reporting)

In release builds, Sentry is used for crash reporting. Transmitted: stack trace, iOS version, device model, app version — no personal data, no session content. Legal basis: Art. 6(1)(f) GDPR (legitimate interest in stability).

3.4 Umami (audience measurement on this website)

For audience measurement on this website we use Umami — self-hosted on our own server in Germany, with no transfer to third parties. We record the page visited, referring source, browser, operating system, device type, screen resolution, language setting and country of origin. Umami uses no cookies and stores no IP addresses; the data is not combined into a user profile, nor used to recognise you across other websites. Legal basis: Art. 6(1)(f) GDPR (legitimate interest in data-minimising analysis). You may object at any time, for example by using a content or script blocker.

4. HealthKit

Sylph may access Apple Health to write Mindful Minutes and optionally display heart rate and HRV. This permission is opt-in and can be revoked at any time in iOS Settings. Apple manages this data; it never leaves your device.

5. Focus timer, Live Activity and notifications

For each focus session, the focus timer stores the date, planned duration, focus minutes and number of interruptions locally on your device. The Live Activity on the Lock Screen and in the Dynamic Island is updated by the app on the device; no push service or server is used for it. Notifications (daily reminder, end of a focus session or break) are local notifications scheduled on the device; you can turn them off at any time in iOS Settings. On iPhone Duo, Sylph reads the hinge state (closed or open) only to start or pause a focus session. In the anonymous usage statistics (section 3.2), a focus session records only the planned duration, how many minutes it ran and whether it was started by closing the phone.

6. Apple App Store

The in-app purchase goes directly through Apple. Apple shares only anonymous aggregate statistics with us. See Apple’s terms for their privacy practices.

7. Your rights

You have rights to access, rectification, erasure, restriction of processing and data portability (Articles 15–20 GDPR). Because we do not store plain identifiers, direct attribution may not always be possible. Requests: [email protected].

8. Right to lodge a complaint

You may lodge a complaint with a data protection authority — e.g. the State Commissioner for Data Protection and Freedom of Information of Rhineland-Palatinate, Germany.

9. Changes to this policy

We may update this policy when we add features or services. The current version is at sylph.appstellar.de/en/privacy/.