A private period tracker, by design
Period data is some of the most sensitive information on a phone. Cycella is a free Android period tracker built so there is less of it to leak or sell in the first place. This page lists what that means in practice.
What "private" means in Cycella
- No account. Cycella never asks for your name, email or phone number.
- No ads, no analytics, no trackers. We do not sell, rent or trade data.
- Stored on your phone. Logs stay encrypted on the phone by default, and Android's own cloud backup is switched off for the app.
- Works offline. Logging and predictions need no internet or mobile data.
- PIN lock. Lock the app with a PIN or fingerprint, useful on a shared family phone.
- Optional encrypted backup. Off until you turn it on. Your data is encrypted on your phone before upload, so our server stores a file it cannot read.
- Delete any time. Me › Delete all my data clears your phone and removes any backup and partner boxes from our server.
What reaches our server, and when
Only if you switch on backup or partner sharing. Even then it is encrypted on your phone first. Our hosting provider can see the network address of a request, as with any internet service, and our code uses it only for a few minutes to limit abuse and does not log or save it. The full list is in our privacy policy, written in plain words.
How the encryption works, in plain words
- On your phone. Your logs are kept in an encrypted database on the phone. Android's own cloud backup is switched off for Cycella.
- Backup. Your phone makes a random key. Your data is locked with it on the phone, and only the locked file is uploaded. The key is shown to you as 12 words and a QR code. Our server never receives the key.
- A copy of the key in your Google or Apple account. So that a new phone can restore your backup, Cycella keeps a copy of the key in your Google account (Android Block Store) or iCloud Keychain from the first time you open the app. If you set an app PIN, that copy is locked with your PIN plus a secret on our server, and the secret is deleted after 10 wrong PIN tries. Without an app PIN, anyone who gets into your Google or Apple account could restore your backup, so we suggest setting a PIN.
- Partner sharing. The two phones agree on a key using a one-time code, without sending the key to our server. Only the items you switch on are shared, encrypted end to end between the two phones.
- Under 18. Backup and partner sharing are turned off, so nothing about you is sent to our server.
The trade-off to know about
Because we never have your key, we cannot read your backup and we cannot recover it for you. You can restore it with your 12 words or QR code, or with the key copy in your Google or Apple account. The account copy works only if your phone's Google backup or iCloud Keychain is on. If every copy of the key is lost, the backup cannot be opened by anyone. Keep your 12 words somewhere safe.
What we do not claim
- Not "anonymous": like any internet service, our hosting provider sees a phone's network address when backup or sharing is used. Our code uses it only for a few minutes to limit abuse and does not log or save it.
- Not "completely secure": no system is. If we learn of a security problem that affects you, we will tell you.
- No independent security audit yet, and no legal certification. The details are in our privacy policy; if you find a problem, write to info@pixelridgeweb.com.
- Not a medical device: cycle and ovulation predictions are estimates, not a diagnosis or birth control.
How to judge any period tracker
We do not think you should take our word for it, or any app's. Our article on what to check before trusting a period app lists the questions to ask: does it need an account, who does it share data with, can you delete it, and what does its privacy policy actually say. You can read ours before the app is out.
Questions about privacy
Do I need an account to use Cycella?
No. Cycella never asks for your name, email or phone number, and works fully without an account.
Does Cycella use analytics or show ads?
No. There are no ads, no analytics, no crash-reporting and no tracking tools in Cycella, and we do not sell, rent or trade data. One thing to know: the QR code scanner, used only when you scan a recovery or partner code, uses Google ML Kit, which Google says may send basic device and app details. It does not send the camera picture or the code.
Where is my period data stored?
On your phone, encrypted, by default. Nothing leaves your phone unless you turn on backup or partner sharing. Android’s own cloud backup is switched off for Cycella.
What happens if I turn on backup?
Your data is encrypted on your phone before upload. The server stores only the encrypted file and never gets the key, so it cannot read it. You open the backup with your 12 words or QR code, or with the copy of the key in your Google or Apple account.
What if I lose my phone or my 12 words?
You may still be able to restore from the copy of your key in your Google or Apple account, on a new phone signed in to the same account (with your app PIN, if you set one). This works only if your phone’s Google backup or iCloud Keychain is on, and a PIN-locked copy stops working after 10 wrong PIN tries. If every copy of the key is gone, nobody can open the backup, including us.
Does Cycella work without internet?
Yes. Logging and predictions happen on your phone. Internet is only used if you turn on backup or partner sharing.
Can I lock the app?
Yes, with a PIN or fingerprint, which helps on a shared phone.
Cycella is free on Google Play for Android, not yet in the EU or UK. The iPhone version is coming soon. Our period calculators also run entirely in your browser, with nothing sent or stored.