Ebb records your menstrual cycle, predicts when your next period is likely, and reminds you beforehand. It does all of that on your device.
Screenshots use fictional data.
The question "what do they do with my data?" has a boring answer here: nothing, because we never receive it.
- No account, no server, no sync. Everything you log is written to a SQLite database on your device. It only goes anywhere else if you move it yourself — a backup file, or another phone.
- No network access at all. Release builds of Ebb ship without Android's
INTERNETpermission. The app is not promising to keep your data local — Android makes it impossible for it to do anything else, and you can verify that yourself in the app's permission list, which is short: notifications (reminders), camera (only while receiving from another phone; nothing is recorded or kept), and restarting reminders after a reboot. - Nothing to sell. No analytics, no advertising, no third-party SDKs. There is no copy of your data for anyone to buy, subpoena, or leak, including us.
- Excluded from cloud backup. Ebb opts out of Android's automatic backup so your history isn't silently copied to a cloud drive.
- Erasable instantly. Delete your data in Settings, or uninstall the app. Ebb keeps no other copy; the only ones are backups you saved or phones you sent your history to yourself.
- Auditable. Open source under the GNU GPL. Published builds are made from this code.
The trade-off, stated plainly: there is no cloud backup, so a lost phone means lost history. Export a backup from Settings if that matters to you.
Ebb is a normal health app for a normal biological process. It doesn't disguise its name or icon, doesn't hide its notifications, and doesn't ask you to treat your own cycle as a secret. See docs/privacy.md for the full statement of what we do and don't mean by "private".
Cycles vary — through stress, illness, travel, perimenopause, or no reason at all. Ebb estimates your next period from your own recent history and tells you how confident it is, rather than presenting a guess as a fact:
- With no history it says so, and falls back on a typical 28-day cycle.
- With a little history the estimate stays close to that average, because one or two cycles aren't much evidence.
- With six or more cycles the estimate is essentially your own rhythm.
- If your cycles vary a lot, Ebb shows a wider window and says as much.
The method is plain arithmetic — a shrinkage-weighted median of your recent cycle lengths — chosen so it can be explained rather than because it's clever.
- Back up to a file — Settings → Back up to a file saves everything as a plain, documented JSON file, wherever you choose. Restore from a backup reads it back.
- Phone to phone — Settings → Send to another phone shows your history as a short series of QR codes; on the new phone, Receive from another phone scans them. Nothing goes over a network: one phone shows, the other looks. This is the only time Ebb asks for the camera.
Ebb is built for one person first, and with one person you'll never see any of this.
If you're helping someone else keep track — a child who's just starting, say — go to Settings → Track someone else too and give them a name. It only asks for a name, and a nickname or initial is fine. Then:
- The title becomes a switcher. Tap it to change whose cycle you're looking at, or to add someone else. History, predictions and the buttons all follow whoever is selected, and speak about them by name ("Sam's period started today").
- You stay "You". You can set a name for yourself in Settings, which helps on a shared tablet, but the app still talks to you as "you".
- Everyone has their own settings. Reminders are off for people you add, until you turn them on. The fertile-window estimate is only ever offered for your own cycle, never for someone you add.
- Removing someone (in their settings) erases their history and nobody else's. When you're back to one person, the switcher disappears.
- Backups include everyone on the phone.
- Handing someone over. When someone gets their own phone, open Settings → Send to another phone and choose just them. On their phone, Receive from another phone: on a fresh install their history simply becomes theirs, and Ebb speaks to them as "you". Afterwards Ebb offers to remove them from your phone — it never does so on its own, because it can't know the other phone got everything. Receiving one person on a phone that already has history offers to add them as someone new instead of replacing anything.
Early. Working: logging (including after the fact), prediction, history, excluding an unusual cycle from predictions, local reminders, backup and restore, phone-to-phone transfer, and tracking more than one person.
Ebb speaks German, Spanish, French, Italian, Portuguese (Portugal) and Russian, each a first draft that needs a native speaker before release. Fix the words yourself on Hosted Weblate, in the browser with no Git needed, or check them in the running app: the preview and what to look for are at ebb.superdavelab.com/beta. A language Ebb doesn't speak yet is welcome too; see docs/translating.md.
Ebb costs nothing, and nothing in the app asks you for money. If you'd like to chip in anyway, you can donate on Liberapay.
Requires the Flutter SDK and the Android SDK.
flutter pub get
flutter test
flutter runTo produce a release APK:
flutter build apk --releaseEbb is a personal tracking tool. It does not provide medical advice, and its fertile-window estimate is derived from cycle timing alone — it is not reliable enough to use as contraception.
Copyright (C) 2026 SuperDaveLab
Ebb is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. It is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See LICENSE for the full text.
Versions up to and including 0.3.0 were released under the MIT licence.