Privacy. Your data, kept small.

Last updated: 8 October 2026

Kaizen is a strength-training app for iPhone, operated by Noé Dubosq (France). This policy explains what the app collects, why, and what you can do about it. Short version: we keep only what's needed to save your training, we never sell data, and there is no advertising or ad tracking.

What stays on your iPhone

The following never leaves your device and is never sent to our servers:

• Body data: sex, age, height and bodyweight entries.
• If you connect Apple Health: the data read (sex, date of birth, height, weight, today's steps and active calories). Kaizen never writes to Health.
• Daily check-ins (sleep and energy). Only the resulting readiness label (for example “ready”) is stored with a workout.
• App preferences such as language, units and appearance.

What we store to back up your training

• Account: when you sign in with Apple, we receive an account identifier and, if you choose to share them, your name and email (which may be an Apple private relay address).
• Training profile: name, language, goal, training days per week, session length, weak points and weight increments.
• Training data: routines, custom exercises, workouts, sets, personal records and plateau history.

We use this data only to run the app: sync your training across devices and compute your next targets. It is hosted by Convex in the European Union (Ireland).

Subscriptions

Purchases are processed by Apple; we never see your payment details. We use RevenueCat to check whether your account has Kaizen Pro. RevenueCat receives an anonymous app user ID and your purchase history from Apple.

Usage statistics and errors

To learn which features are actually used and to fix bugs, the app sends usage events to PostHog (hosted in the EU): screens opened, workout started or finished (duration, number of sets), check-in done, weight logged, paywall viewed, purchase, and app errors. These events are linked to your account ID, never to your name or email.

No body data is sent: no weight, height, age, sex or check-in answers. These statistics are not used for advertising and are never combined with data from other apps or websites.

Support messages

If you contact us through the support form, we store your email, optional name and message to answer you, and delete them once the request is closed or after 12 months at the latest.

Your rights

• Export: Profile → Settings → Export my data gives you a copy of your training data.
• Delete: Profile → Settings → Delete account deletes your account right away, and your training data from our servers within minutes. Deleting the app removes the data stored on your iPhone.
• Under the GDPR you can also ask to access, correct or restrict your data, and complain to the CNIL (cnil.fr). Write to us through the support form.

Children

Kaizen is not directed at children under 13 and we do not knowingly collect their data.

Changes

If this policy changes, we'll update the date above and, for meaningful changes, tell you in the app.