Privacy Policy

Onyx · Last updated 26 September 2026

This policy explains what personal data the Onyx workout tracker ("the app") handles, why, and what choices you have. The app is developed by 4ft3rh0urs, based in the Netherlands, which is responsible for your data. If you have a question about privacy, e-mail optroot.store@outlook.com.

1. What data the app handles

Your account

Your e-mail address and password, used to sign in and to send you a password reset e-mail when you ask for one. Passwords are stored hashed by our authentication provider. We can't see them.

What you log

Workouts: title, date, duration, notes, and for each exercise its sets with reps, weight or time.
Routines: the name, exercises and order of the routines you save.
Body weight: the weights you log and when you logged them.

Stored only on your phone

Your settings, such as kg or lb.
A draft of the workout you're logging, saved every few seconds so it isn't lost if the app closes. It's deleted when you finish or discard the workout.

Calorie estimates are calculated on your phone from your workout and aren't stored separately.

What we don't collect

The app doesn't use advertising, analytics or tracking tools. It doesn't collect your location, contacts or data from other health apps, and it doesn't sell or share data with advertisers or data brokers.

2. Why we use it

We use your data only to provide the app: to show your workouts, routines and progress, and to keep them backed up to your account so you get them back when you sign in on another phone. The legal basis is the agreement between you and us to provide the app (Article 6(1)(b) GDPR).

Body weight can count as health data. You choose whether to log it, and by logging it you agree that the app stores it for you (Article 9(2)(a) GDPR). You can delete any entry at any time, and we never use it for anything other than showing it to you.

3. Where the data is stored

Your data is stored in a database on your phone, so the app works offline. When you're signed in, it's also synced over an encrypted connection (HTTPS) to our cloud database, provided by Supabase, which acts as our processor. Access rules in the database make sure only you can read or change your own data.

4. How long we keep data

We keep your data for as long as you have an account. You can delete individual workouts, routines and body weight entries at any time. When you delete your account (Settings → Delete account), your account and all data linked to it are removed from our cloud database and from your phone.

5. Your rights

Under the GDPR you have the right to access, correct, delete or export your personal data, to object to or restrict how it's used, and to withdraw your consent for body weight data at any time. To use these rights, e-mail optroot.store@outlook.com. You can also file a complaint with the Dutch data protection authority, the Autoriteit Persoonsgegevens.

6. Security

Data is sent over encrypted connections, and each account can only access its own data. No system is perfectly secure, but we take reasonable measures to protect your data and will inform you if a breach affects you.

7. Children

The app is not intended for children under 16.

8. Changes

If this policy changes, we'll update the date at the top of this page. For important changes, we'll also let you know in the app.

9. Contact

4ft3rh0urs, the Netherlands · optroot.store@outlook.com