Privacy Policy

Cythr ("we", "our", "us") is a free cycle-tracking application. We take your privacy seriously — especially when it comes to sensitive health data. This policy explains what data we collect, why, and how we protect it.

1. Data We Collect

Account Data

• Email address (for authentication)
• Display name (optional)
• Profile avatar (optional)
• Authentication tokens (securely stored)

Health & Cycle Data

• Menstrual cycle dates, phases, and predictions
• Symptoms and their severity
• Mood entries and intensity
• Free-text health notes
• Medication and supplement reminders (e.g. contraceptive pills)
• Water intake, meditation, and wellness data

Health Integrations (Optional)

If you choose to connect Apple Health or Google Fit, we may access:

• Step count and physical activity
• Sleep duration
• Heart rate data

This data is only accessed with your explicit permission and is never shared with third parties.

AI Features (Opt-in)

AI-powered smart logging and insights are <strong>off by default</strong>. We only send data to a third-party AI provider after you explicitly enable AI features in Settings → AI Features. You can revoke this consent at any time. When AI is enabled:

• Your messages, logged symptoms, moods, and notes are sent to <strong>Anthropic PBC</strong> (Claude) — a US-based AI provider — to generate responses and insights. Anthropic is contractually bound to not train on your data (zero-retention agreement)
• No personally identifiable information (email, name, account ID, payment data) is sent to Anthropic
• Only cycle-relative dates (not absolute calendar dates) and the data fields you logged are shared
• AI conversation history is automatically deleted after 30 days. Disabling AI in Settings stops all future data transmission immediately

2. How We Use Your Data

• Provide cycle tracking, predictions, and health insights
• Generate personalized AI-powered recommendations
• Enable partner sharing features (only with your consent)
• Send medication/supplement reminders you configure
• Improve app functionality and fix bugs

We do not sell your data. We do not use your health data for advertising.

3. Health Information Disclaimer

The data collected by Cythr is intended solely for personal wellness tracking and informational purposes. It is not intended for clinical use, medical diagnosis, or treatment decisions.

Cycle predictions, phase estimates, and AI-generated insights are algorithmic calculations based on user-entered data. They are not medical diagnoses and have not been clinically validated.

For the complete health information disclaimer, please refer to Section 3 of our Terms of Service.

4. Data Storage & Security

• All data is encrypted in transit (TLS/HTTPS)
• Passwords are hashed using industry-standard algorithms
• Refresh tokens are stored as SHA-256 hashes
• Database hosted on secure infrastructure with restricted access
• Avatar images stored in encrypted object storage

5. Data Sharing

We share your data only in these cases:

• Partner sharing: Cycle data shared with a partner you explicitly link
• AI processing: Anonymized health context sent to AI providers (no PII)
• Legal requirements: If required by law

6. Your Rights

You have the right to:

• Access all data we store about you
• Export your data in a portable format
• Delete your account and all associated data
• Revoke health integration permissions at any time
• Opt out of AI features

To request data deletion, use the in-app settings or contact us at privacy@cythr.com.

7. Children's Privacy

Cythr is not intended for children under 13. We do not knowingly collect data from children under 13. If you believe we have collected such data, please contact us immediately.

8. Changes to This Policy

We may update this policy from time to time. We will notify you of significant changes through the app or via email. Continued use of Cythr after changes constitutes acceptance of the updated policy.

9. Contact

For privacy-related questions or requests:
privacy@cythr.com