ZenFast — Privacy Policy
ZenFast ("the app", "we") is a fasting + weight-loss tracker built local-first. This policy explains, in plain language, what data the app handles and what it does NOT do. It is written to be accurate to how the app actually works — not boilerplate.
The short version
- Your data stays on your phone. Your fasts, weight, food log, sleep, steps, workouts, body measurements, and settings are stored only in local storage on your device. We do not run a server that receives them. We cannot read them.
- No account. No sign-up. You do not create an account or give us an email to use the app.
- No cloud sync, no data sale, no ad tracking. We do not upload, sell, rent, or share your health or personal data with anyone, and we do not use advertising or analytics trackers that profile you.
- You can export or delete everything yourself, any time, from Settings (Backup & Restore) or by uninstalling the app (which removes all local data).
What the app stores (locally, on your device)
- Fasting history, active fast, and goals
- Body weight + measurements and weight unit preference
- Food log, saved meals, recipes, nutrition profile (sex, age, height, activity, target rate)
- Steps, workouts, water/caffeine counters, meal schedule
- Sleep log (hours you enter) and your chronotype quiz answers/result — used to compute sleep debt, your energy day-plan and forecasts, all on-device
- Streak calendar marks (rest / sick / travel days, streak freezes, repairs)
- Grocery lists built from your recipes, and your equipment/training preferences
- Course progress and your private course reflections — reflections are visible only to you, are never included in the shareable CSV export, and travel only inside the JSON backup file you create
- Hunger-moment timestamps (to compute your personal "hardest hour")
- App preferences and which milestone badges you've earned
All of the above is kept on-device using your phone's app storage. It is included in the local backup file only if you choose to export it, and that file goes wherever you send it (you control that).
Device permissions
- Notifications — used to send your fasting reminders, stage milestones, the optional persistent "live fast" notification, and meal/eating-window reminders. All scheduled locally on your device; no push server is involved. You can turn these off in your system settings or in the app.
- The app does not request access to your contacts, location, camera, or microphone.
Purchases (when paid plans are enabled)
ZenFast is pay-once (no recurring subscription required for the lifetime plan). When you buy a plan, the purchase is processed by Google Play Billing and managed through RevenueCat (our purchase infrastructure). These services receive only what's needed to process and validate the purchase (e.g. a purchase token and an anonymous app-user identifier) — never your fasting, weight, food, or health data. See Google Play's and RevenueCat's privacy policies for how they handle billing data.
Until paid plans are live, the app runs in early-access mode and no purchase data is sent.
Smart insights are computed on your device
ZenFast's "smart insights" — the pattern discovery, forecasts, anomaly and trend detection, and the ranked feed — are produced by plain on-device math (statistics and a small local model). There is no AI service, no cloud processing, and no data sent off your phone to generate them. They are computed from your own logs, on your device, every time you open the screen.
Health data
The fasting, weight, sleep, and nutrition information you enter is health-related and personal. Because it never leaves your device (except in a backup file you create), we never transmit or process it on our side. ZenFast is an educational and tracking tool, not medical advice — talk to a licensed physician before starting intermittent fasting, especially if you are pregnant, nursing, under 18, diabetic, or have a history of disordered eating.
Children
ZenFast is not directed to children. Weight-loss/deficit features are hard-blocked for users under 18.
Data retention & deletion
Your data lives on your device until you delete it. To remove everything: use Settings → Backup & Restore to manage it, or uninstall the app to erase all local data permanently.
Changes to this policy
If the app's data practices change (for example, if an optional cloud or AI feature is added later), we will update this policy and surface the change in-app before the feature is enabled.
Contact
Questions about privacy: aispotlightlab@gmail.com (Lex Oleksiienko, Calgary, Alberta, Canada). Governed by Canadian privacy law (PIPEDA) and applicable local regulations.