Privacy Policy

Last updated: April 3, 2026

Your privacy matters more than our features. Here is exactly what Sereno does, and does not do, with your data.

What Data We Access

Sereno reads the following data from Apple HealthKit to calculate your stress score:

  • Heart Rate Variability (HRV): the primary signal for your stress score
  • Heart Rate: detects spikes and recovery patterns
  • Sleep Data: duration, stages, and quality metrics
  • Activity Data: steps, workouts, and movement patterns
  • Respiratory Rate: additional stress indicator when available

Each data type serves a specific purpose in your stress score calculation. We do not access any data beyond what is listed above.

What Stays on Your Device

All of your health data stays on your iPhone. It is never uploaded to our servers, never sent to third parties, and never leaves your device.

We never upload your health data. Your heart rate, HRV, sleep, and activity data are processed entirely on your device.

Sereno uses Apple's SwiftData framework for local storage. Your stress scores, sleep sessions, and daily summaries are stored in a private database on your phone that only the Sereno app can access.

What We Collect Anonymously

We collect a small amount of anonymous data to keep Sereno running smoothly:

  • Usage analytics (Cloudflare Web Analytics): cookieless. Counts page views on our website without identifying you. No cookies, no fingerprinting, no personal data.
  • Crash reports (Firebase Crashlytics): if the app crashes, an anonymous report helps us fix bugs. No health data is included.
  • Optional diagnostic reports: if you choose to send a diagnostic report from the app, it includes device model, app version, and error logs. Never health data.

None of these services can identify you personally. We do not have user accounts, emails, or login credentials.

GDPR Compliance

If you are in the European Economic Area (EEA), the UK, or Switzerland, you have specific rights under the General Data Protection Regulation:

Your Rights

  • Right to access: request a copy of data we hold about you
  • Right to rectification: correct inaccurate data
  • Right to erasure: request deletion of your data
  • Right to data portability: receive your data in a machine-readable format
  • Right to restrict processing: limit how we use your data
  • Right to object: object to processing based on legitimate interest

Legal Basis

  • Health data: Explicit consent (Article 9(2)(a) GDPR). You grant consent when you authorize HealthKit access.
  • Analytics: Legitimate interest (Article 6(1)(f) GDPR). Cloudflare Web Analytics is cookieless and privacy-preserving.
  • Crash reporting: Legitimate interest for service reliability.

You have the right to lodge a complaint with your local Data Protection Authority.

Contact us at support@serenoai.app. We will respond within 30 days.

KVKK Compliance

Sereno is developed by a Turkish developer. If you are in Turkey, you have rights under the Personal Data Protection Law (KVKK, Law No. 6698):

Your Rights Under KVKK

  • Learn whether your personal data is processed
  • Request information about processing if processed
  • Learn the purpose of processing and whether it is used in accordance with its purpose
  • Know third parties to whom data is transferred
  • Request correction of incomplete or incorrect data
  • Request deletion or destruction of data under conditions set forth in Article 7
  • Object to a result that is to your detriment arising from analysis of data exclusively by automated systems

Data controller: BSBApps (sole proprietorship), Turkey

VERBIS note: VERBIS registration status and number will be listed here when applicable.

For KVKK requests: support@serenoai.app

Health Data Specifically

Because Sereno is a health-related app, we want to be exceptionally clear about how we handle sensitive health information:

Your health data is never sold. Never shared with advertisers. Never used for profiling. Never uploaded to any server.

  • HealthKit data is read-only: Sereno reads your health data to calculate scores but does not write back to HealthKit (except breathing session completion)
  • No server-side health data storage: all processing happens on-device
  • No health data in analytics: our crash reports and analytics never contain heart rate, HRV, sleep, or activity information
  • No health data in AI requests: when Sereno generates AI insights, it sends only your stress score (a single number 0-100), never raw health metrics
  • Apple HealthKit guidelines compliance: we follow Apple's strict HealthKit data use policies

We believe your health data belongs to you. It lives on your device, under your control.

Third-Party Services

Sereno uses the following third-party services. None of them receive your health data:

Service Provider Purpose Data Shared Health Data?
Crashlytics Firebase (Google) Crash reporting Device model, OS version, crash stack traces Never
Web Analytics Cloudflare Website traffic Cookieless page view counts Never
AI Gateway Cloudflare Workers AI insights Stress score (0-100), no raw health data Never
App Store Apple Distribution, billing Purchase info handled by Apple Never
HealthKit Apple Data source Stays on device, Apple controls access Read-only, on-device

We choose our partners carefully. Every service listed above has its own privacy policy and data handling commitments.

Children's Privacy

Sereno is not directed at children under the age of 13 (or 16 in the EEA). We do not knowingly collect personal information from children. If you believe a child has provided us with personal data, please contact us at support@serenoai.app and we will delete it.

Data Retention

Your health data is stored locally on your device for as long as the app is installed. Deleting the Sereno app removes all locally stored data.

  • Anonymous analytics data is retained by Cloudflare for a maximum of 30 days
  • Crash reports are retained by Firebase for 90 days
  • Diagnostic reports (if submitted) are retained for 90 days, then automatically deleted

How to delete all your Sereno data: delete the app from your iPhone. All local data (scores, sleep sessions, insights) is removed immediately. No server-side data remains because we never uploaded it.

Contact

If you have questions about this privacy policy or how Sereno handles your data:

We aim to respond to all privacy inquiries within 30 days.

Changes to This Policy

We may update this privacy policy from time to time. When we do:

  • We will update the "Last updated" date at the top of this page
  • For significant changes, we will notify you through the app
  • Continued use of Sereno after changes constitutes acceptance

We encourage you to review this page periodically.