Underhook is a Brazilian Jiu-Jitsu training app. This policy explains what
information the app handles, why, and the choices you have. We keep it short
and plain because that is the honest way to write one.
What we handle
Account & sign-in. You start anonymously. If you choose
to sign in — with Google on Android, with Apple on iPhone — that provider gives us
a private identifier, your email address, and your name where you allow it, so your
progress can follow you across devices. Authentication is managed through our
backend provider, Supabase.
Training data. Your lesson progress, belt and stripes, XP,
streaks, and per-question performance are stored so we can sync your account and
personalize which questions you see.
Profile. An optional display name, and an optional academy,
country, or city if you enter them.
Photos & camera (optional). If you take a training
check-in photo, it stays on your device and is only used to render your shareable
check-in card — it is never uploaded to our servers. If you add a profile avatar,
that image is stored in our secure storage until you replace it or delete your
account. You can remove either at any time.
Purchases. Subscriptions and one-time purchases are processed
by the store you bought from — Google Play on Android, Apple on iPhone. We receive
your purchase status to unlock Pro features. We never receive your payment card
details.
App activity. Which screens and lessons you open, and the
results of your sessions, together with the app version, language, a random
install identifier, and the country of your App Store or Google Play account (to
count users by country; never your location). It is our own analytics, used to fix
and improve the app; there is no third-party advertising or tracking SDK in the
app.
Diagnostics. Minimal technical logs to operate and debug the app.
What other players see
The app has a weekly board where players race on XP. Everyone who earns XP in a
week is on it, and other players see your first name and the initial of your last
name (or your belt, if you have not set a name), the belt you train at, your academy
and its country, your profile photo if you added one, your XP, and how many weeks in
a row you have trained. Nothing else from your account is shown. You can take
yourself off every board in Settings → Show me on boards.
What we do not do
We do not collect face data or any biometric data. Photos you take or choose
are used only as your check-in card image or profile avatar — they are never
scanned, analyzed, or used for face recognition or any other processing.
We do not sell your personal data.
We do not use third-party advertising SDKs, and we do not show ads.
Who we share with
Only the service providers needed to run the app: our backend/database host
(Supabase), Google (for Sign in with Google and for processing Google Play purchases)
and Apple (for Sign in with Apple and for processing App Store purchases). The
in-app rival's after-fight comment is written by a language model provider (Anthropic)
on our behalf: what we send is the fight itself — the score, the win/loss record and
which skills went wrong — and never your name, email or account identifier.
Retention & your choices
Your account data is retained while your account is active. You can delete your
account and all associated data directly in the app: Settings → Account →
Delete Account. Deletion permanently removes your profile, training progress, and any
stored avatar from our servers. Deleting the app removes data stored on your device.
You can also request access to, or deletion of, the data in your account by
contacting us at the address below — the full instructions, including deletion by
email if you no longer have the app installed, are on
this page.
Children
Underhook is not directed to children under 13.
Changes
If this policy changes, we will post the update here with a new effective date.