Privacy Policy

Last updated: 3 November 2026

The short version

Everything you log stays on your phone, apart from what you choose to export and what Android may back up to your own Google account. There is no account, no sign-up, and no server of ours. We cannot see your diary, because there is nowhere for it to go.

Apart from a routine check for app updates, one thing leaves your phone. Tideline uses a subscription service called RevenueCat, and the app sends it an anonymous ID and your subscription details so it can tell whether you have subscribed. It never sends anything you log. The details are under Payments.

This policy is longer than that only because "your diary stays on your phone" is a claim worth spelling out, and so is its one exception.

What we collect

We run no server, so nothing you log reaches us. The only information collected at all is subscription information, and RevenueCat collects it for us — see Payments.

Specifically, Tideline does not collect, transmit, sell, or share:

• your foods and symptoms, or any notes, tags, times, or grades attached to them
• your weight, how your legs feel, or your glucose readings
• your phase markers, or the dates your periods started
• your name, email address, phone number, or an account of any kind
• your location
• your contacts, photos, calendar, or files
• advertising identifiers

There is no analytics SDK, no advertising SDK, no crash-reporting SDK, and no attribution SDK in this app. Apart from Expo's library for app updates, the one third-party SDK that connects to the internet is RevenueCat's, for subscriptions. We have deliberately not added others, and we do not intend to. Google Play's own console tells us how many people installed the app; that, and the subscription figures described under Payments, is all the measurement we get and all we want.

Where your data lives

On your device, in four places:

• Diary databases. Everything you log is stored in database files in Tideline's private app storage, which Android keeps isolated from other apps: your foods and symptoms (with their tags, amounts, notes, times, and grades); your daily measurements (weight, how your legs feel, glucose); your phase markers; and the dates your periods started, plus the flare window if you set one. Some of this is health information. It stays here.
• A small settings store holding the date your 30-day trial began and the last answer about whether you have a subscription.
• The RevenueCat SDK's own storage: the anonymous ID it generated for this install and a saved copy of your latest subscription status.
• Temporary export files. When you export, Tideline first writes the file to its own private cache folder, then hands it to Android's share sheet. The file stays there until Android clears the cache; Tideline does not delete it after sharing.

All of it is removed when you uninstall the app.

Device backups

If you have Android's automatic backup switched on for your Google account, the operating system may include Tideline's data — the diary databases and the settings store — in your device backup, the same way it does for other apps. That backup is made by Android, sent to your own Google account, and governed by Google's privacy policy — not by us. It exists so that your diary survives getting a new phone.

We never receive that backup and cannot read it. If you would rather it did not happen, you can turn backups off for this app in Android's Settings, under System → Backup.

Apart from the subscription information under Payments, this is the one way your data can leave your device without you choosing to send it, so it is worth knowing about.

Sharing and exporting

You can export what you have logged: a full JSON backup and CSV files of your foods and symptoms, and separate CSV files for your measurements, phase markers, and period starts. When you do, Android's share sheet hands that file to whatever app you pick — email, cloud storage, a messaging app, a file manager.

Once a file leaves Tideline that way, it is subject to the privacy policy of wherever you sent it, not this one. Export files contain the entries they cover, in full. Treat them accordingly.

Importing a backup reads a file you choose on your phone. Nothing is uploaded.

Internet access

Logging, patterns, and exports all work without a connection, in airplane mode included. Apart from a routine check for app updates, the only network requests Tideline makes are the subscription requests to RevenueCat described under Payments, and none of them carries anything you log. If RevenueCat cannot be reached, Tideline uses the last subscription answer stored on your device.

The app declares Android's INTERNET permission for those requests; the framework it is built with (React Native) also expects it. Apart from RevenueCat's SDK and the update check, the app's code has no network client. The links in the app — this policy, the terms, and the support email — are handed to your browser or mail app when you tap them; Tideline itself sends nothing.

Payments

Tideline is free to use in full for 30 days. After that, logging new entries and viewing patterns needs a subscription, bought through Google Play. Google processes the payment; we never see your card details, billing address, or Google account. Google's handling of that transaction is covered by Google's privacy policy and the Google Play Terms of Service.

To find out whether you have subscribed, Tideline uses RevenueCat, a subscription service whose SDK is built into the app. RevenueCat processes the information below on our behalf. Apart from a routine check for app updates, it is the only data Tideline itself sends anywhere, and the only data Tideline collects:

• a random anonymous ID, generated on your phone. It is not linked to your name, email, or Google account; Tideline never gives RevenueCat any of those
• your purchase and subscription details: which subscription, your Google Play purchase token, and whether it is active
• technical information: your device type and operating system, your locale and currency code (used to show prices), and when the app was last used
• as with any internet request, your device's network address

None of it includes anything you log, and Tideline sends RevenueCat no advertising ID, name, email, or other account details. Tideline uses none of RevenueCat's advertising or attribution features, and RevenueCat's optional diagnostic reporting is switched off. The information is sent when Tideline starts and when you subscribe or restore a purchase, and again from time to time while the app is open to keep your status current. RevenueCat encrypts it in transit and handles it under its own privacy policy.

We use it to keep subscriptions working and to see subscription figures, such as how many people subscribe. We do not sell it or share it with anyone else.

Children

Tideline is a general-purpose diary and is not directed at children. We do not knowingly collect personal information from children. Apart from a routine check for app updates, the only data Tideline itself sends anywhere, for anyone, is the anonymous subscription information described under Payments.

Your rights

We do not hold your diary, so the usual data rights — access, correction, portability, erasure — are not requests you need to make to us. For your diary you already have all of them, directly, inside the app:

• Access and portability: export a JSON backup and CSV files of your foods and symptoms, and CSV files of your measurements, phase markers, and period starts, at any time.
• Erasure: "Delete all my data" in the app's Data screen permanently erases your foods, symptoms, measurements, phase markers, and period starts from the device. Uninstalling removes everything Tideline stored on the phone. Neither removes an Android backup already made to your Google account, or a file you exported.
• Correction: edit or delete individual food and symptom entries; delete a measurement, phase marker, or period start and log it again.

The one exception is the subscription record held by RevenueCat (see Payments). Deleting your data in the app does not delete it, and the app has no way to. It carries a random ID and Google Play purchase details, not your name or email. If you have questions about it, write to support@makektm.com.

If you are in the UK, EU, or another region with data-protection law: we never receive your diary, so there is no diary data for you to enforce a right against us over. The subscription record is processed on our behalf by RevenueCat, so questions about it can come to us.

Changes to this policy

If this policy changes materially, the date at the top changes with it, and the updated version is published at https://tideline.makektm.com/privacy.html. Because the app links to the hosted copy rather than embedding one, you always see the current version.

Contact

Questions about this policy: support@makektm.com

Tideline is not a medical device and does not diagnose, treat, cure, or prevent any medical condition. It shows you patterns in what you chose to log — nothing more. Always consult a qualified healthcare professional for medical advice, diagnosis, or treatment.

The current version of this document is published at https://tideline.makektm.com/privacy.html.