Flux
Privacy policy
Flux app and fluxbudget.fr website · updated October 14, 2026
English translation. This page translates the politique de confidentialité, written in French. If the two versions differ, the French version prevails.
In short. Flux asks for no account, no email address and no bank connection. Your budget data stays on your phone. The app contains no ads and no tracking tools, and we sell no data. The fluxbudget.fr website counts its visits without cookies, with a tool we host ourselves (see “Website audience measurement”).
Who we are
Flux is published by Paul Janisson, Toulouse, France. Contact: contact@fluxbudget.fr. See also the legal notice (in French).
What data, where, and who can read it?
| Data | Where it is | Who can read it |
|---|---|---|
| Transactions, fixed bills, budgets, savings pots, game progress (streak, badges…) | Only on your device | You |
| Notes and receipt photos you add to an expense (optional) | Only on your device; inside the encrypted sync if you turn it on | You |
| Dictating an expense (optional, off by default): your voice, for the length of the sentence | Handled by your phone’s speech recognition (Google on Android, Apple on iPhone), under their own rules; Flux only receives the text, which stays on your device | Your phone’s speech recognition service; never us |
| Anonymous purchase identifier and, if you subscribe, Flux+ purchase history | On Android: an anonymous identifier, which the app sends to RevenueCat (our subscription management provider) when it opens and when you come back to it, even without a subscription; the purchase history at Google Play and RevenueCat if you subscribe. On iPhone: nothing, the app contains no purchase. | They and we: subscription status, never your budget data |
| Flux+ subscription taken on the web: email address, name on the card, country, payment method, invoices | Stripe (our payment provider), which collects them itself on its secure payment page | Stripe, and us for the email address and invoices (subscription management, accounting); never card numbers. The email address also goes through Brevo, to send you your subscription confirmation |
| Flux+ subscription taken on the web: random subscriber identifier created by the app, Stripe customer and subscription numbers, end date of the paid period | Your device (inside the encrypted sync if you turn it on); on our server at o2switch (France), a record filed under a hash of the identifier | Us, to activate Flux+ and open your “Manage my subscription” page; never your budget data |
| Encrypted sync (Flux+, if you turn it on): an encrypted block, its version number, the date it was sent | Our server at o2switch (France) | No one: it is encrypted on your device with a key only you have |
| Creator code (optional): entered for the 30-day challenge, taken from a fluxbudget.fr/?code=… link, or read from the Google Play install link (Install Referrer, read on your device) | Your device; sent to RevenueCat only if you subscribe | Us, to pay the creator |
| Invite code (optional): your code, if you invite a friend; the code of the person who invited you, if you tap the button to get your streak freeze and say thanks | Our server at o2switch (France): a simple counter per code (the number of friends who joined), with no IP address, no device identifier, no date | The person who invited you sees this number in their app, to receive their streak freezes |
| Email address and origin (for example “insta”), if you sign up on fluxbudget.fr/bientot to hear when Flux comes out on the App Store or Google Play | Brevo (our email provider, France, data kept in the European Union) | Us, to write to you about it |
| Android app test: the address of the Google account you use to join the testers group | Google (Google Groups and Google Play Console), under its own rules; at Brevo for people who signed up for the test with the old form, before October 11, 2026 | Us, to open the test to your account and write to you about it |
| Technical connection data for the website (IP address, date) | Our host’s logs (o2switch, France) | The host, for the security of the service |
Check it yourself
In the app, Profile → What Flux sends gives the full list of what goes out to the Internet, depending on what you turned on. On Android, an app such as PCAPdroid shows every connection an app makes; on iPhone, the App Privacy Report (Settings, then Privacy & Security) lists the domains each app contacts: you can compare. In the web app, the page’s security policy (CSP) only allows connections to fluxbudget.fr: your browser blocks everything else, even if we wanted otherwise.
Sync between devices (Flux+)
Sync is optional. If you turn it on, your data is encrypted on your device (AES-256) before anything is sent, with a key only you have and that never leaves your devices. Our server, hosted in France at o2switch, only keeps an unreadable block, with no account, no email address and no link to your identity: we cannot read it. If you lose your key, no one can decrypt it.
With each upload, the Android app also sends the anonymous RevenueCat purchase identifier, so the server can check with RevenueCat that your Flux+ subscription is active. This identifier is not stored: the server only keeps the date until which the subscription was checked. If you subscribed on the web, your random web subscriber identifier is sent instead, and the server checks it against its own record, without calling any third party.
You can erase the block from the server at any time from the app (Profile → Encrypted sync → erase my data from the server).
What stays on your phone
- Reminders: notifications scheduled by the app on your phone (or by your browser, for the web app). No server sends them.
- Fingerprint or face lock: your phone checks on its own and answers Flux with a yes or a no. Flux never sees your face, your fingerprint or your passcode.
- Widgets (Android and iPhone) and Apple Watch: they show figures the app leaves for them on the phone; the watch receives them directly from your iPhone, without going through the Internet.
- Apple Pay payments logged automatically (optional, set up in the Shortcuts app): the amount and the merchant name go from Shortcuts to Flux, on your iPhone. Nothing leaves it.
Launch sign-up and Android test
The fluxbudget.fr/bientot page offers two separate things:
- Hearing when Flux comes out on the App Store or Google Play: you leave your email address and tick a box. You receive an email to confirm your address, a welcome email sent automatically after confirmation, then an email on the day Flux comes out on the App Store, and another on the day it comes out on Google Play.
- Testing the Android app before its release: since October 11, 2026, you join the Google testers group with the Google account of your phone, then become a tester on Google Play, which only opens the test to group members. These steps take place at Google, under its own rules. People who signed up before that date with the old form stay on the testers list at Brevo until they unsubscribe, and receive a few updates about the test.
For the launch, your consent is confirmed by a click in an email (double opt-in): without that click, the address is not kept. Our server keeps no address: it only counts the number of sign-ups of the day, to limit sending. We also note where the sign-up came from (for example “insta”), to know where Flux gets known. This data is kept by Brevo, never on our server, and is never matched with your budget data, which stays on your device. It is never sold or used for advertising.
Website audience measurement
Since October 5, 2026, the website pages (home page, guides, press page, waiting page and legal pages) count their visits with Matomo, free software installed on our own server, stats.fluxbudget.fr, hosted in France at o2switch. It tells us which pages are read and where visitors come from (a search engine, Instagram, TikTok).
- It sets no cookies and does not follow you from one site to another.
- Your IP address is truncated by its last 2 bytes before anything is recorded, and your browser’s “Do Not Track” setting is respected.
- The detailed visit log is turned off: we only see totals (number of visits, pages read, origin).
- Traffic data is passed on to no third party and is used for no advertising.
- It knows nothing about your budget: the Flux app contains no audience measurement, neither in its web version (fluxbudget.fr/app), nor on Android, nor on iPhone.
Legal basis: our legitimate interest in knowing how the website is used. To object, write to contact@fluxbudget.fr; a content blocker also prevents this measurement, without affecting how the website reads.
Why this data (legal bases, GDPR)
- Performance of a contract: managing your Flux+ subscription, and collecting payment through Stripe if it is taken on the web.
- Legal obligation: keeping invoices for subscriptions taken on the web.
- Legitimate interest: measuring subscriptions in aggregate (RevenueCat statistics) and crediting a subscription to the creator whose code you used.
- Consent: launch sign-up (box ticked and confirmed by email) and Android test sign-up, which you can withdraw at any time with the unsubscribe link in each email, or by leaving the testers group.
- Legitimate interest (security): the host’s technical logs (IP address, date), to protect the website and the sync relay against abuse.
How long
- Budget data: as long as you keep the app; uninstalling it or using “Erase everything” deletes it.
- Subscription data: for the length of the subscription, then according to accounting obligations (10 years for accounting records).
- Encrypted sync block: until you erase it from the app; blocks inactive for more than 18 months may be deleted.
- Launch and test addresses: until you unsubscribe, and at the latest one year after the app comes out on both the App Store and Google Play (whichever is later).
- Website technical logs: a few days.
Transfers outside the European Union
The website, the web app and the sync relay are hosted in France. However, RevenueCat, Inc. is based in the United States: on Android, it receives the anonymous purchase identifier, as well as the technical data of each connection (IP address, system, app version). For a subscription taken on the web, Stripe (Stripe Payments Europe, Ltd., Ireland) may also transfer payment data to Stripe, Inc. (United States). These transfers only concern subscription, payment and connection data (purchase status, purchase identifiers, any creator code), never your budget data. They are covered, depending on the case, by the EU–US Data Privacy Framework or by the standard contractual clauses adopted by the European Commission.
Google (Google Play) and Apple (App Store) distribute the app and may process, outside the European Union, data related to your Google or Apple account, under their own rules. Flux receives no budget data from them.
Your rights
You can ask for access to, correction, erasure or portability of your data, or object to its processing, by writing to contact@fluxbudget.fr. You can also contact the French data protection authority, the CNIL. Since your budget data is not with us, you export it yourself from the app (Profile → export a backup) and erase it with “Erase everything”.
Providers
- Apple (App Store): distribution of the iPhone app.
- Google (Google Play): distribution of the Android app, and payment of subscriptions taken on Android when sales are open; Google Groups for the Android testers group.
- RevenueCat, Inc. (United States): management of subscriptions taken on Android.
- Stripe (Stripe Payments Europe, Ltd., Ireland): payment of subscriptions taken on the web.
- Brevo (Sendinblue SAS, France, data kept in the European Union): sending launch sign-up emails, test updates to people who signed up with the old form, and the confirmation of a subscription taken on the web.
- o2switch (France): hosting of this website and of the sync relay.
Sales of Flux+ have been suspended since October 5, 2026: no new subscription can be taken. Current subscriptions continue under the terms of sale (in French).
Audience
Flux is intended for people aged 18 and over.
Changes
If anything changes, this page is updated and the date at the top changes. Significant changes are mentioned in the app’s release notes.
See also, in French: politique de confidentialité (prevails) · terms of sale · legal notice.