Effective: 21 September 2026 · Last updated: 21 September 2026
Duetling is a baby tracker. You log feeds, sleep, nappy changes and growth for your baby, and if you choose to, share that log with one other parent. This page explains exactly what is stored, where it goes, and how to get rid of it.
Duetling is an independent app. For anything in this policy, including privacy requests, contact nestlog7@gmail.com.
Everything you log is written to a database on your device, and that copy is the source of truth. It is why the app works on a plane, in a lift, or with no signal at 3am. Your device's operating system encrypts this storage at the file level; the app does not add its own encryption layer on top.
If you create an account, your household's data also syncs to a server we run on Supabase (a hosted PostgreSQL platform). Everything in transit is encrypted over HTTPS. Access is enforced by row-level security in the database, which means a query can only return rows belonging to a household you are a member of — not merely that the app avoids asking for other rows.
The app is fully usable signed out. Create an account only if you want to:
If you sign out, the app keeps working and your local log stays on the phone.
| Data | Notes |
|---|---|
| Baby's name | Required to create a baby. |
| Date of birth | Optional. Used for the age shown on Home and for growth charts. |
| Sex | Optional — male, female, or unspecified. |
| Feeds | Time, method (breast, bottle or solids), side, volume, food description. |
| Sleep | Start and end times. |
| Nappy changes | Time and kind (wet, dirty, both). |
| Growth | Weight, height and head circumference, with the date measured. |
| Pumping, medicine, temperature, notes | Time, plus the amount, dose, reading or text you enter. |
| Household name | Only if you create or rename one. |
There is no way to attach a photo of your baby in the app, and we never ask for one. We also do not ask for your own name, your address, your phone number, or your baby's medical records.
| Data | Why |
|---|---|
| Email address | Only if you create an account. Used to sign you in, to recover access, and to let your partner invite you. Held by Supabase's authentication service. |
| Notification token | If you sign in, the app registers a Firebase Cloud Messaging token so the other parent's phone can be told there is something new to fetch. The message itself carries no details of what was logged — it is a “check now” signal, and your phone then fetches the change over the same encrypted connection as everything else. The token is deleted with your account. |
| App preferences | Theme, language, units, and similar. Stored on your device. |
| Crash reports | Stack trace, device model and OS version when the app crashes or recovers from an error. No advertising identifier, and nothing you logged. |
| Usage statistics | Which screens are opened and which features are used. Never includes the content of an entry. |
Google AdMob serves ads in the free version. The Google Mobile Ads SDK collects your device's advertising identifier and standard ad-request information. In regions where consent is required, the app shows Google's consent form before any ad request is made, and you can change that choice later in Settings. Pro users see no ads at all, so no advertising identifier is collected from them.
Google Play Billing handles the one-time Pro purchase. Google tells the app whether a purchase exists; we never see your card details, and payment is entirely between you and Google.
Firebase Crashlytics (Google) collects a crash report when the app crashes or hits an error it recovers from: the stack trace, the device model, the operating system version, and how far into the session it happened. It does not collect an advertising identifier, and it does not contain anything you logged. This is on whenever the app has crash reporting configured, because without it a crash is invisible to us — the first we would hear of it is a one-star review that cannot be acted on.
Firebase Analytics (Google) collects anonymous usage statistics: which screens are opened, how often an entry is logged, whether a feature is used at all. It tells us which parts of the app are actually used and which are ignored. It is not tied to your account, and it is never joined to anything you logged.
No analytics event contains anything you typed. "A feed was logged" is a statistic about the app. The volume, the side, the time, the note, and your baby's name are yours, and they stay in your own database. That line is enforced in one place in the code, so it cannot erode one convenient parameter at a time.
These four Google services are the only third parties that receive anything. Your baby's log is never shared with any of them, or with anyone else outside your household.
If you invite a second parent, they see the full log for the babies in your household: every entry, who logged it, and when. That is the point of the feature. Sharing happens only through our server — there is no peer-to-peer or local-network path, and every byte that leaves your phone goes to Supabase over HTTPS.
Either parent can leave the household at any time from Settings.
Deleting an individual entry hides it immediately everywhere and marks it as deleted so the deletion reaches your partner's phone too. Deleting your account is what removes data outright.
In the app: Settings → Delete account. This removes your account and your data from our server permanently, and it cannot be undone.
If you cannot get into the app, see the deletion page.
One thing worth knowing before you delete. If your household has a second parent, the household and its entries survive so their copy is not destroyed along with yours. Your membership is removed and the entries you logged stop being attributed to you. If you are the only member, everything goes.
Your Pro unlock belongs to your Google Play account rather than to your Duetling account, so deleting your Duetling account does not cost you the purchase.
Duetling is for parents and carers, not for children. We do not knowingly collect data from anyone under 13.
The app does hold information about an infant, entered by their parent. That is the entire purpose of a baby tracker, and it is why the log is never shared outside your household and never sent to advertisers.
Duetling records what you tell it and shows you the pattern. It does not diagnose, advise or interpret. Growth charts plot the measurements you enter; they are not a clinical assessment. If you are worried about your baby, speak to a doctor or health visitor.
Depending on where you live, you may have the right to access, correct, export or erase your data, and to object to certain processing.
For anything else, email nestlog7@gmail.com.
Our Supabase project is hosted in the European Union. If you use the app elsewhere, your data is transferred there and stored under that jurisdiction's protections.
If we change this policy we will update the date at the top. Material changes — anything that widens what we collect or who receives it — will also be announced in the app before they take effect.