Privacy Policy

Courtesy translation. The French version is the official one; if the two differ, the French text prevails.

Last updated: 4 September 2026

This policy describes what data Bachelier Maths (the "App") processes, in its iOS and Android versions, why, and what you can require of us.

Summary

The App works without an account: no email address, no password, no phone number.
Your progress (answers, sessions, streak, trophies) stays on your device. We hold no copy of it.
Only three things leave your device: anonymous usage measurement, the error reports you choose to send, and, if you have picked a school, your score for the Guerre des lycées leaderboard.
No advertising, no advertising trackers, no sale or commercial sharing of data.
Purchases go through your phone's app store (the App Store or Google Play): we never see your payment details.

1. Who processes your data

The data controller is Brocko Studio Ltd, 61 Bridge Street, Kington HR5 3DJ, United Kingdom, publisher of Bachelier Maths.

For any question about this policy, or to exercise your rights: admin@bachelier.app.

2. What stays on your device

Almost everything the App produces never leaves it. The following is stored locally, in the App's private storage:

your question-by-question progress and your session history;
your streak, your trophies and your statistics;
your year group, the chapters you have enabled and your settings;
your scratch pad drawings;
your progress through the past papers and the automatismes, and your Chrono scores;
the nickname you choose for the friend challenge.

None of this is transmitted to anyone. It is gone when you delete the App, and you can erase it at any time from Settings → "Réinitialiser ma progression".

As with any app, if your phone is backed up (to iCloud, to Google's backup service, or to a computer), this data is included in that backup. The backup is yours: it is made and protected by Apple or by Google depending on your device, and we have no access to it.

3. What leaves your device

None of the cases below carries your identity: no name, no email address, no phone number. The detail is set out so that you can check it point by point.

3.1 Usage measurement

So that we know which features are actually used, the App sends events such as "session completed", "trophy unlocked" or "subscription page opened". Each event carries its type, your declared year group (Première or Terminale), the training mode concerned, and the App and operating-system version numbers.

These events are processed by TelemetryDeck, a measurement service hosted in the European Union. The technical identifier attached to them is double-hashed before it is sent: it is not reversible and does not let us trace an individual. No name and no address are transmitted. Neither is any advertising identifier: not Apple's IDFA on iOS, nor Google's advertising ID on Android, which the App does not read. And it performs no tracking of your activity across apps or across sites, on either platform.

The content of your answers is never transmitted: we know how many questions a session contained, not which ones you got wrong.

3.2 Error reports

When you use "Signaler une erreur" on a question or an exercise, we receive the question identifier, the chapter concerned, the category you selected, any free-text comment you wrote, and the App and operating-system version numbers (which are the whole diagnosis for a display problem).

No device identifier and no IP address is stored with the report: it reaches us with no sender attached. The comment is a free-text field, and only your description of the problem is useful to us, so there is no need to put anything about yourself in it.

3.3 Guerre des lycées

This feature is optional and only becomes active if you pick a school. If you do, the App transmits a random identifier created at install time, the national school code (UAI) and your score, together with a security token used to reject fabricated scores.

iOS. The security token is provided by Apple's App Attest service.

Android. Guerre des lycées is not offered in the Android app. If it is added, this policy will be updated to state the security mechanism used, which cannot be Apple's.

That random identifier is not linked to any personal information: it contains no name, no email address, and no platform-provided device identifier. The published leaderboard ranks schools; no individual student appears in it.

3.4 Subscriptions and purchases

Subscriptions and the lifetime purchase are sold by your phone's app store, never by us. Payment, billing and renewal are handled by that store: we receive neither your payment details nor the payment method attached to your account.

iOS. The sale is made by Apple through the App Store, and we do not receive your Apple Account identifier.

Android. The sale is made by Google through Google Play, and we do not receive your Google account.

In both cases the App only checks, with that store and on the device, whether an active subscription grants you access to premium content.

4. The friend challenge

A challenge sent to a friend passes through no server: everything is encoded in the link itself, including the nickname you chose and the scores of the round. The nickname therefore travels with the link and stays visible to whoever receives it, which is what a nickname is for rather than a full name.

5. Notifications

Reminders (daily training, streak at risk, inactivity nudges) are scheduled locally by your device. They pass through no server, and no remote-notification token is sent to us. You can decline them when permission is requested, or turn them off later in your phone's settings.

6. What we do not do

No accounts, therefore no user directory.
No advertising, in the App or on the site.
No sale, rental or sharing of data for commercial purposes.
No advertising profiling and no automated decision-making producing legal effects concerning you.
No collection of special category data within the meaning of Article 9 GDPR.
No access to your location, your contacts, your microphone or your camera.

7. The bachelier.app website

The site uses Cloudflare Web Analytics, a cookie-free, aggregated audience measurement (page views, referrers). That is why the site shows no consent banner: it sets no measurement or advertising cookie.

Download links to the app store carry a campaign parameter recording which page of the site you clicked from. It contains no personal data and only tells us which pages are useful.

The /android page offers to take an email address so we can tell you when the Android version ships. That list has a single purpose: sending that one message. It is not a newsletter, it is used for nothing else, and it is deleted once the launch message has gone out. You can ask to be removed at any time by email.

Like any website, bachelier.app technically receives visitors' IP addresses, processed transiently by our host to serve pages and block abuse. We do not retain them in our databases.

8. YouTube and our publishing tool

Bachelier publishes educational videos on its own YouTube channel. To upload them we use an internal tool built on YouTube API Services. Those services require us to tell you so, which is what this section is for.

That tool processes no data about you. It runs in environments of our own — our machine, or a private container we control — with our own Google account, and does exactly two things: put our videos on our channel, with their title and description, and post our own first comment under them. It reads no other channel, reads no comments, stores no YouTube data, and has no users: nobody but us signs in to it.

The Bachelier Maths app itself uses no YouTube API Services. Its settings offer a link to our channel; if you open it you leave the app, and YouTube's own privacy policy applies from there.

In using these services we are bound by the YouTube Terms of Service, and data Google collects on its side falls under the Google Privacy Policy. The access granted to our tool can be revoked at any time from the Google account permissions page of the account that granted it, which is ours: you have no access of your own to revoke.

9. Legal bases

Providing the App and managing premium access: performance of a contract (Article 6(1)(b) GDPR).
Aggregated usage measurement, handling reports, security and fraud prevention: legitimate interests (Article 6(1)(f)), our interest being to maintain and improve a reliable service, balanced against collection kept minimal and non-identifying.
Guerre des lycées: performance of a contract for the feature you enable yourself, and legitimate interests for the anti-fraud check.
Android waiting list: your consent (Article 6(1)(a)), withdrawable at any time.

10. Retention

Local data: until you delete the App or reset your progress.
Error reports: kept for as long as it takes to handle them, then archived editorially so that we keep a record of the content corrections made.
Guerre des lycées: the score row is kept for the current season; at the end of the season, only a per-school aggregated ranking is archived.
Android waiting list: deleted after the launch message has been sent.
Usage measurement: retained by TelemetryDeck in accordance with that service's retention policy, in non-identifying form.

11. Recipients and processors

We disclose your data to no one other than the providers needed to run the service:

Apple: App distribution on iOS, subscriptions and purchases, device attestation.
Google: App distribution on Android through Google Play, subscriptions and purchases.
TelemetryDeck: usage measurement, servers located in the European Union.
Cloudflare: hosting for the site, the technical endpoints and the database that receives reports and scores.
Resend: sending the Android launch email, to the people on the waiting list only.

We may also disclose data where the law requires it.

12. Transfers outside the European Union

Usage measurement is hosted in the European Union. Our other providers may process data from countries outside the Union; those transfers are framed by the European Commission's standard contractual clauses or by another recognised mechanism. The data controller is established in the United Kingdom, a country covered by an adequacy decision of the European Commission.

13. Minors

Bachelier Maths is aimed at lycée students, and therefore often at minors. That is precisely why the App asks for no account, no identity, and no data capable of identifying a student.

If you are under 15, talk to a parent or guardian before using the App, and in particular before making any purchase. A parent or guardian may write to admin@bachelier.app with any question or request concerning their child's data.

14. Your rights

You have the right of access, rectification, erasure, restriction, objection and portability in respect of your data. To exercise them, write to admin@bachelier.app.

In practice there is little to ask for: we hold no account and no identifier attached to a person, so there is no file in your name here, and that is precisely the point (the GDPR does not require us to collect additional information for the sole purpose of identifying you). Concretely:

your local data is entirely in your hands, inside the App;
for the Guerre des lycées, write to us: we will tell you how to find the row corresponding to your install, and we will delete it;
for the Android waiting list, simply ask us to remove your address.

If you believe your rights are not being respected, you may lodge a complaint with the CNIL (www.cnil.fr) if you live in France, or with the supervisory authority of your country of residence.

15. Changes

This policy may change, in particular if we add a feature that changes what is processed. The date at the top of the page always shows the last update.

16. Contact

Brocko Studio Ltd, 61 Bridge Street, Kington HR5 3DJ, United Kingdom: admin@bachelier.app.

In the app, Settings → “Nous contacter” prepares that message for you. It is not sent automatically: your mail app opens, and nothing leaves your device until you tap Send. The message is pre-filled with a short technical block — app and operating-system versions, device model, language and time zone, your chosen settings, and a few counters from your progress — so that a problem can be reproduced without you having to describe it. The block is visible in the message: you can read it, remove any part of it, or delete it entirely before sending.