Privacy
Last updated 24 September 2026
Halcyon is an app for menopause and HRT, made by Luka Kapetanovic (Two Brick Labs). This page is the policy, in plain words.
Halcyon is a diary. It is not a medical device, it does not diagnose or treat anything, and it is not for emergencies. See the Terms.
Who is responsible
Luka Kapetanovic, an independent developer based in Serbia who trades as Two Brick Labs ("we" on this page), is the data controller for Halcyon. Your logs are stored on servers in the EU. Serbia has its own data protection law modelled on the GDPR; where we handle data of people in the EU or UK, the GDPR and UK GDPR apply to us too. Questions or requests: support@twobricklabs.com.
Address: Jurija Gagarina 197, 11070 Novi Beograd, Belgrade, Serbia.
What we collect
You sign in with Apple or Google. We keep an account id so we know it is you. There is no password.
We store what you put in Halcyon: symptoms, treatments, doses, bleeding, cycles, appointments, notes, and settings.
These are health data. Under EU and UK law they are a special category, so we only process them because you asked us to by using Halcyon, and with your explicit consent given when you first set up the app. You can withdraw that consent at any time by deleting your account.
If you connect Apple Health, Halcyon reads sleep, steps, and resting heart rate on your phone to show them beside your logs. We only read; we never write to Apple Health. Those readings stay on your phone and are not sent to our servers.
Subscriptions are handled by Apple or Google. We never see your card. RevenueCat, our subscription provider, receives your purchase status and a random account id so we know your subscription is active. It never receives your logs.
Usage analytics are off unless you turn them on in the app’s privacy settings (“Share anonymous usage data”). If you do, PostHog (EU cloud) receives an anonymous device id, the names of the screens you open and a few app events. Never your logs, symptoms, treatments or notes. You can turn it off at any time, and the id is then deleted from your phone.
If you turn on reminders, they are scheduled on your phone. Lock-screen text leaves out medication names and doses.
Where your logs live
Your logs are saved to your Halcyon account on our servers in the EU, so they follow you to a new phone. The phone keeps a copy so you can still log when you are offline.
We do not sell your logs. We do not use them for ads. We do not share them with insurers, employers, or advertisers. We do not use them to train AI models.
We share data only with the providers named on this page, only as far as they need it to run the service, and only under contracts that stop them using it for anything else.
Who helps us run Halcyon
- Neon (database, EU – Frankfurt): stores your account and logs.
- Cloudflare (servers): carries data between the app and the database.
- RevenueCat (subscriptions): your purchase status and a random account id.
- PostHog (EU, only if you turn on usage data): anonymous usage events.
- Expo (app updates): your phone’s IP address and app version when the app checks for updates.
- Apple and Google: sign-in and payments, under their own privacy policies.
Data outside the EU
Neon, Cloudflare, RevenueCat and Expo are US companies. Where data they handle leaves the EU or UK, it is protected by the European Commission’s Standard Contractual Clauses and, where the company is certified, the EU-US Data Privacy Framework.
Why we may use your data
Health logs: your explicit consent, and providing the app you asked for. Account and subscription: providing the service under our Terms. Usage analytics: your consent, off by default. Security logs: our legitimate interest in keeping the service safe.
Server logs
Our servers keep short technical logs (time, IP address, errors; never what you log) to keep the service running and secure. We keep them for no more than 30 days.
The clinician summary
The PDF you export is made on your phone. Where you send it, and to whom, is your choice and your responsibility. We do not receive a copy.
How long we keep it
For as long as you keep your account. When you delete your account we erase it from our servers within 30 days, and from backups within 90 days.
Your rights
You can see and export everything we hold about you in Settings, and correct any entry in the app. You can delete everything, as below. You can also ask us by email for a copy in a reusable format, to correct or erase your data, to restrict or stop using it, or object to how we use it. You can withdraw consent at any time: turn off usage data, or delete your account. We answer within one month. You can also complain to a data protection authority: in Serbia the Commissioner for Information of Public Importance and Personal Data Protection, in the EU your local authority, and in the UK the ICO.
How to delete
In Halcyon, go to Settings and tap Delete account. That erases your account and every log. It cannot be undone.
Signing out only removes Halcyon from that phone. Your account stays until you delete it.
If you get a new phone, sign in with the same Apple or Google account, then delete from there if you want everything gone.
Face ID
Face ID only unlocks the app on that phone. It is not how we store your logs.
Age
Halcyon is for adults. We do not knowingly collect data from anyone under 18. If you believe a child has used Halcyon, email us and we will delete the account.
Changes
If we change this policy in a way that matters, we will tell you in the app before it takes effect.