Privacy
Privacy Policy
Fjell is made by David van Rooij ("we"). This policy explains, in plain words, what the app handles, why, and how to delete it.
Effective 1 October 2026
In short
- Fjell collects no personal data. The app itself sends nothing about you to us or to anyone else.
- No account, no sign-in, no analytics, no ads, no tracking and no third-party SDKs. Fjell is built only with Apple's own frameworks.
- Your data stays on your iPhone and in Apple Health. We, the developer, never receive it.
What stays on your iPhone
Fjell stores a few things on your iPhone so it can work. Fjell has no server, so they go nowhere else.
- Your workouts. For each session of 1 min or longer: when it started and ended, the plan, the max heart rate it used, the rounds you finished, your heart rate during the session, average and peak heart rate, and time in zone. History, streaks and the recap are built from these.
- Your settings. Your plan and zones, how your max heart rate is set, your sound settings and your weekly goal.
Recovery is worked out on your iPhone from your Apple Health data when you look at it; Fjell keeps no copy.
Fjell does not ask for your location, contacts, photos, camera or microphone.
If you back up your iPhone to iCloud or a computer, the backup includes Fjell's data, as it does for other apps. Apple handles those backups; we cannot see them.
Links to research papers in the app open in your web browser. Those sites have their own privacy policies.
Apple Health
Fjell uses Apple Health only with your permission, and only for the reasons below. You choose what to allow when Fjell asks, and you can change it at any time.
What Fjell reads
| Data | Why |
|---|---|
| Date of birth | To work out your age for the age formula, 208 − 0.7 × age, used for an automatic max heart rate. |
| Heart rate | To find your best 30-second heart rate in the last 6 months, used for an automatic max heart rate. Fjell looks only at readings of 120 bpm or more. |
| Heart rate variability and sleep | For Recovery: your overnight heart rate variability against your own baseline. Fjell reads enough nights to compare the weeks before your first session with the time since, at most 800 days. |
What Fjell writes
- Workouts. Each session of 1 min or longer is saved to Apple Health as a workout, with each stage marked and, as workout details, the plan, the zones and max heart rate it used and how the session went. With Timer only, your iPhone saves a plain workout without heart rate.
- On Apple Watch, Fjell asks to read and write heart rate, active energy, distance (walking and running, cycling, cross-country skiing) and workouts. It uses them to record the workout you are doing, then saves the workout to Apple Health with what your Watch measured.
Your Health data is never used for advertising, never sold, never sent to us and never shared with anyone.
Apple Watch and the lock screen
Heart rate is measured on your Watch and sent to your iPhone over Apple's own connection between your devices, not to any server. Fjell on Apple Watch keeps nothing of its own: the workout goes to Apple Health.
During a workout, Fjell's Live Activity shows the stage, time left and your heart rate on the lock screen and in the Dynamic Island, where anyone who can see your iPhone can see them. To turn it off, open Settings, tap Apps, then Fjell, and turn off Live Activities.
Purchases
Subscriptions are handled by Apple. We get no payment details and no personal information about you: Apple gives us sales figures, not names. Deleting the app does not cancel a subscription; you manage it in Settings, under your name, then Subscriptions.
Crash reports
If you have chosen to share analytics with app developers (Settings > Privacy & Security > Analytics & Improvements > Share With App Developers), Apple may pass crash reports and usage totals for Fjell on to us. We use them only to find and fix bugs. You can turn this off at any time in the same place.
When iOS gives Fjell its own crash and performance reports, Fjell keeps them on your iPhone and never sends them anywhere.
When you email us
If you email us, we receive your email address and what you write. We use it only to answer you, and we delete it when it is no longer needed. Ask us and we will delete it sooner.
How to delete your data
- One workout: in History, press and hold the workout, then tap Delete. This removes it from Fjell. The copy in Apple Health stays.
- Health access: in the Health app, tap your picture, then Apps, then Fjell, and turn off what you no longer want to share. You can also find this in Settings > Privacy & Security > Health.
- Everything Fjell keeps: delete the app. This removes its workouts and settings from your iPhone.
- Workouts in Apple Health: workouts Fjell saved stay in Apple Health until you delete them in the Health app.
This website
This website sets no cookies, runs no analytics and loads nothing from other companies. Like most web hosts, ours may keep standard server logs, such as your IP address and the pages you request, for a short time for security. We do not use them to identify you.
Children
Fjell is not made for children, and it collects no personal data from anyone, children included.
Your rights
Because Fjell sends us nothing, we hold no data about you from the app to give you, correct or delete. It is on your devices, where you control it. For emails you sent us, ask and we will send you a copy or delete them. If you live where data protection laws give you more rights, such as the EU or the UK, you keep all of them, including the right to complain to your data protection authority.
Changes to this policy
If this policy changes, we will post the new version on this page with a new effective date. Fjell will not start collecting personal data without saying so here first.
Who is responsible
David van Rooij makes Fjell and is responsible for this policy. Questions are welcome at [email protected].