Privacy Policy — StackUp

Last updated: 30 September 2026

StackUp ("the app") is a workout tracker for Android, made by Undisputed Development (Alexander Papenfuß), Germany. StackUp Web (app.stackupgym.com) is its companion in the browser. This policy explains what data both handle. In short: without an account, StackUp collects nothing and your data never leaves your device. With an optional account, your training log is stored on our server so it can sync between your devices and be shown in StackUp Web — and you can export it or delete it, in the app, at any time.

Without an account

StackUp does not require an account, a sign-in, or any personal information. Everything you enter — your exercises, splits, workout sessions, weights, reps, body weight and settings — is stored locally on your device in a private app database. It is not uploaded to us or to anyone else. When you uninstall the app, this local data is removed by the operating system.

You can create a backup file or an export file from Settings; those files go wherever you send them and are yours.

With an account (optional)

You can sign in with Google to keep your training log in sync across your devices. If you do, we store the following on our server:

• Account and sign-in data: the identifier Google assigns to your Google account for StackUp, your e-mail address and display name as Google provides them, and a name for each device you signed in on (for example "Pixel 8 Pro"). We never receive your Google password.
• Your training log: your exercises, splits, workout sessions and sets, body-weight entries, and the training preferences from Settings (units, rep ranges, rest timer). Your theme and other device-only settings stay on the device.
• Technical records: our server logs each request with its date, the IP address it came from and the account it was for, so we can keep the service running and find abuse. These logs are rotated within days.

We use this data for exactly one thing: to provide the sync you signed in for, and StackUp Web if you use it. There is no advertising, no analytics service and no tracking in StackUp, and we do not sell, share or transfer your data to anyone. The only third party involved is Google, which handles the sign-in itself under Google's own privacy policy.

Where: on a server we operate in Germany (European Union).

How long: for as long as your account exists. When you delete your account, your data is removed from the server immediately; copies in our server backups expire within 14 days.

Legal basis (GDPR): performance of the service you asked for by signing in (Art. 6(1)(b)).

StackUp Web (app.stackupgym.com)

StackUp Web shows the same account's training log in a browser. When you sign in there, with the same Google account, we also process:

• A signed-in browser: a cookie that keeps you signed in. It holds a random value; our server stores only a hash of it, with the date you last used it, for 30 days after your last visit. With it we store a short label for the browser, such as "Chrome · Windows", taken from what your browser reports when you sign in. The full browser identification itself is not stored. Your account page lists these browsers together with your phones.
• A sign-in in progress: a second cookie, and on our server the random values Google's sign-in needs to be secure. Both are deleted when the sign-in completes, and after ten minutes at the latest.

StackUp Web sets no other cookies, loads nothing from other servers (its fonts and images come from StackUp Web itself), and runs no analytics. That is why it has no cookie banner: the two cookies are strictly necessary for the sign-in you asked for (§ 25(2) no. 2 TDDDG). The public pages set no cookie at all. Google receives your visit only when you press "Sign in with Google" and choose an account on Google's own page.

Your rights, and how to use them

• See and take your data: Settings → Data → Export data (JSON) gives you your entire training log as one file in an open format.
• Delete your account and your data on our server: in the app, Settings → Account → ⋮ → Delete account permanently; or in StackUp Web, Account → Delete your account. This removes the account and everything stored for it, immediately, and signs out every phone and browser. The log on your device stays yours.
• If you can no longer use the app (for example after uninstalling it), e-mail us at the address below from the e-mail address of your Google account and we will delete the account for you. Instructions are also at https://undisputed-dev.com/stackup/delete-account.html.
• You also have the rights to rectification, restriction and objection under the GDPR, and to complain to a supervisory authority. Contact us first and we will sort it out.

Children's privacy

StackUp is not directed at children and does not knowingly collect any data from anyone under 16.

Contact

Questions about this policy or your data: feedback.stackup@undisputed-dev.com.

Changes to this policy

If this policy changes, the updated version will be published at this same URL with a new "Last updated" date.