Your data belongs to you
DayByDay is built on a simple promise: your health data is yours. We store it securely, we never sell it, and we never use it for advertising. You can export everything you've entered, or delete your account and everything you logged from Settings at any time (see 'Deleting your account' below for the few things we keep).
No ads. No data selling. Ever.
DayByDay earns revenue through subscriptions only. Your health data is never shared with advertisers, data brokers, or any third party for commercial purposes.
What we collect
We collect only what you choose to enter into the app, plus the basics required to run your account.
- ✦Account info — your name and email address.
- ✦Health data you log — weight, body fat, sleep, GLP-1 doses, exercise, body measurements, labs, nutrition, water, mood, blood pressure, blood glucose, and symptoms.
- ✦App settings — your preferred units, goals, and appearance (theme) preferences.
- ✦Subscription status — whether you're on Free, Core, or Plus, managed via the App Store or web billing. We never see your payment card details.
We do not collect your location, browser history, or any data from other apps beyond what you explicitly sync via Apple Health.
How your data is stored
Your data is encrypted in transit using TLS (the same standard banks use) and encrypted at rest on our servers. We use Supabase (PostgreSQL) hosted on US-based servers. Every database table is protected by Row-Level Security, which means your records are mathematically inaccessible to other users — even if they tried.
Row-Level Security
Every piece of data in DayByDay is scoped to your account with Row-Level Security enforced at the database level. No other user can read your records without your credentials.
Third-party services we use
DayByDay relies on a small number of trusted services to run. Here's exactly what each one does with your data — and just as importantly, what it doesn't.
| Service | Purpose | What they see |
|---|---|---|
| Supabase | Database hosting | Your encrypted health data, stored on US servers. |
| Anthropic (Claude) | Powers Dayo, your AI coach | The relevant slices of your logged data are processed to generate your coaching insights. Used only to write your notes — never sold, never used to train models or for advertising. |
| RevenueCat | Subscription billing | Your billing status only (Free / Core / Plus). Not your health data. |
| Apple Health | Health data sync (iOS) | Health data is read from your device's local store. It never leaves your phone via Apple's systems. |
| App Store / web billing | Subscription payments | Your purchase history and subscription status. DayByDay never sees your card number. |
| Meta (advertising pixel) | Measures our ads | Visits to our public website and sign-up pages, never what you log in the app. The app has no third-party analytics or ad tracking. |
How Dayo uses your data
When Dayo writes your daily read or weekly story, the relevant facts from your data are sent to Anthropic's Claude to compose the note, then the result is saved to your account. That's the only purpose. Your data isn't used to train AI models, isn't sold, and isn't used for advertising. Dayo is part of Core and Plus — if you're on the Free plan, this processing doesn't happen.
Apple Health data stays on your device
When you connect Apple Health, DayByDay reads data from your device's local HealthKit store and syncs it to your DayByDay account on Supabase. Apple itself does not receive your DayByDay account data. Apple Health data is never used for advertising.
Medical disclaimer
DayByDay is not a medical device
DayByDay is a personal wellness tracking application. It is not FDA-cleared, CE-marked, or approved for diagnostic, clinical, or therapeutic use. No data, metric, or estimate shown in the app constitutes a medical diagnosis, prognosis, or prescription. Always consult a qualified healthcare provider before making changes to your medications, diet, or health regimen.
The charts, trend lines, predictions, scores, and Dayo's coaching notes you see in DayByDay are all calculated or composed from data you enter. They're meant to help you understand your own patterns over time. They are not clinical measurements.
Not a substitute for medical advice
No diagnosis. No treatment. No cure.
DayByDay does not diagnose, treat, prevent, or cure any medical condition. GLP-1 medication tracking is informational only — the medication level estimate is based on pharmacokinetic half-life data, not a blood measurement. Blood oxygen readings from consumer wearables are not equivalent to clinical pulse oximetry. Do not use DayByDay data to make clinical decisions.
If you're experiencing a medical emergency, call 911 or your local emergency number immediately. DayByDay is not a crisis or emergency tool.
Your rights (GDPR & CCPA)
Depending on where you live, you have legal rights over your personal data. DayByDay honors these rights for all users, regardless of location.
- ✦Right to access — Request a copy of all data we hold about you.
- ✦Right to export — Export any of your data as CSV, or a full Health Report PDF, from You → Reports & Export.
- ✦Right to correction — Edit or correct any inaccurate data directly in the app.
- ✦Right to deletion — Delete your account from Settings → Account → Delete Account & All Data. See 'Deleting your account' below for exactly what is removed and what we keep.
- ✦Right to restrict processing — Contact us to restrict how your data is used.
- ✦Right to object — You can object to any data processing at any time.
Contact us about your data
To exercise any of the rights above, or to ask questions about your data, email us at support@mydaybyday.app. We respond within 30 days as required by GDPR. For CCPA requests, we respond within 45 days.
Deleting your account
You can delete your account at any time from Settings → Account → Delete Account & All Data. Deleting your account removes your profile and everything you logged (weight, medication, sleep, food and water, measurements, labs, mood, symptoms and more), your photos, and your sign-in account. It starts the moment you confirm and finishes within minutes. It can't be undone. Your App Store subscription is separate: cancel it in iPhone Settings, under your name, then Subscriptions. Anything DayByDay saved into Apple Health stays in Apple Health. Copies in automatic backups are replaced as they expire (about 7 days). We keep three things after deletion: a short record that the account was deleted (its random id and dates, no name or email) for two years; our payment service's purchase record (billing history, no health information); and the staff action log, which is a security record. Emails you sent to support, and files you exported yourself, are not covered by the button.
Deletion can't be undone
Once your account is deleted, your data cannot be recovered. Export your data first (You → Reports & Export) if you'd like to keep a copy.
Deleting your account does not automatically cancel a paid subscription. If you're on Core or Plus, cancel your subscription separately (You → DayByDay Plus/Core → Manage Subscription, or via the App Store) before deleting to avoid future charges.
Data retention after deletion
Your data is removed from our live systems within minutes. Automatic backups roll off in about 7 days (except the few records described above).