Cycle Cipher: Period Tracker

Cycle Cipher is a period and cycle tracker that keeps your records on your phone. There is no account to create and no advertising, and your health entries never reach the developer.

Track your cycle
• Log period days, flow, 14 symptoms, 9 moods, sexual activity, basal body temperature (°C) and a note for each day.
• The calendar marks logged periods, the estimated next period, the estimated fertile window and the estimated ovulation day.
• Insights works out your average cycle and period length from what you log, and shows a chart of recent cycle lengths and your most frequent symptoms.

Health events
Keep a private record of medication abortion, procedural abortion, miscarriage, pregnancy tests, provider visits and contraception changes, with follow-up dates, test results and notes.

Privacy
• The app stores your entries in an encrypted database in its private storage. Android Keystore holds the key. On Android 15 and later, Keystore also refuses to use the key while your phone is locked; Android 11–14 do not provide that same documented restriction for this symmetric-key use.
• Lock the app with a PIN of 4 to 8 digits, with device authentication (biometrics or your screen lock), or with both.
• Cycle Cipher hides its content in the recent apps view.
• Android backup and device-to-device transfer skip Cycle Cipher’s data. To move to a new phone, use an encrypted export.
• No ads, no account and no analytics SDK. The developer runs no server for health data.

Exports
• Export an encrypted JSON file and lock it with a passphrase you choose. Nobody can recover the passphrase, including the developer, so keep it somewhere safe.
• Plaintext JSON and CSV exports are available too. The app warns you first, because anyone who has those files can read them.
• Encrypted backups let you move your records between your own devices.
• Before an import changes anything, a preview shows you what will change.

Reminders
Turn on a period estimate reminder, 1 to 7 days before the estimated start, or an ovulation estimate reminder on the estimated day. Both arrive at 9 a.m. The notification’s title reads “Cycle Cipher reminder”, and neither its title nor its text mentions your period or ovulation.

Languages
English, Deutsch, Español, Français, हिन्दी, 日本語 and 繁體中文. On Android 13 and later you can give the app its own language in system settings.

Optional tips
Every feature works without paying. Four optional tips support development. They unlock nothing, and you can tip more than once. Google Play processes the payment.

Health information
Cycle Cipher is not a medical device and does not diagnose, treat, cure, or prevent any medical condition. Cycle, fertile-window and ovulation estimates come from your past entries and can be early or late, so do not use them as contraception. Consult a healthcare professional for medical advice, diagnosis, or treatment, and get urgent care for severe symptoms.