Effective 27 April 2026
Luff is a weight tracking app developed and operated by an independent developer based in the United Kingdom. This policy explains what data Luff collects, why, and what control you have over it.
Health data. With your permission, Luff reads data from Apple Health. This includes your weight, height, date of birth, and biological sex for your trajectory, as well as active energy burned, resting energy burned, step count, walking and running distance, flights climbed, sleep analysis, and exercise minutes for Insights. Luff also writes weight entries you log back to Apple Health. Your health data is never sent to external servers. It stays on your device and, if you use iCloud, syncs through Apple's CloudKit infrastructure.
Profile information. During setup you enter your goal (lose, maintain, or gain weight), target weight, weekly rate, and activity level. This information is stored on your device and synced via iCloud if enabled.
Usage analytics. Luff collects pseudonymised usage data to understand how people use the app and to improve it. Your identity in analytics is an anonymous identifier with no name or email attached. Analytics are processed by PostHog on servers in the European Union. We track a small number of specific events: when you complete onboarding steps, log a weight, when your drift level changes, and when you open the app. We also store high-level profile properties (your goal, activity level, and whether HealthKit is enabled). Auto-capture is disabled. We only track events we have explicitly defined.
Subscription information. Subscriptions are processed entirely by Apple through the App Store. Luff never sees your payment details. We use RevenueCat to manage subscription status (whether your subscription is active, when it renews, and what plan you are on). RevenueCat receives an anonymous user identifier and subscription metadata only.
Device motion. Luff uses your device's gyroscope to create a subtle parallax effect on the chart. This data exists only in memory while the effect is visible. It is never stored or transmitted. The effect is disabled if you have Reduce Motion enabled.
Luff does not collect your name, email address, phone number, physical address, photos, location, contacts, or advertising identifiers.
| Data | Location |
|---|---|
| Health and profile | On your device + your iCloud account (Apple CloudKit) |
| Analytics events | PostHog, European Union |
| Subscription status | RevenueCat (subscription metadata only) |
| Payment details | Apple (Luff never sees these) |
| Notifications | On your device only |
| Device motion | In memory only, never stored |
Luff uses the following third-party services. Each receives only the data described above.
We do not sell your data to anyone.
Luff does not require an account. There is no email, username, or password. Your identity within Luff is an anonymous identifier from your iCloud account. If you do not use iCloud, a random identifier is generated on your device. This identifier cannot be traced back to you without access to your Apple ID.
Under UK GDPR and EU GDPR, you have the right to:
"Start Over" deletes your data on-device and in iCloud. HealthKit data is managed through Apple Health directly. Deletion of analytics data from PostHog requires contacting us.
If you are a California resident: Luff does not sell personal information. You have the right to know what data is collected (described in this policy) and to request deletion.
Your data is stored until you delete it using "Start Over" or by removing the app. Analytics data is retained per PostHog's retention policy. Subscription records are retained by RevenueCat and Apple as required for billing.
Luff is not intended for anyone under 16. We do not knowingly collect data from children under 16. Because Luff does not collect identifying information, we cannot identify individual users in our systems. Data stored on-device and in iCloud can be removed by using "Start Over" in the app or deleting the app.
If we update this policy, the revised version will be posted here with a new effective date. Continued use of Luff after changes are posted constitutes acceptance of the updated policy.