Privacy

In short: this website uses no analytics or advertising services and embeds no third-party content. It only sets a cookie if you choose to log in to an account – and then just a strictly necessary login cookie. Fonts and all other files are served from our own server.

Controller#

Daniel Herzog, c/o POSTFLEX PFX-384-519, Emsdettener Straße 10, 48268 Greven, Germany Email: info@butterflymarketinsider.com

Server log files#

When you visit a page, your browser necessarily transmits data to our server. The following is stored in log files: IP address, date and time, requested address, status code, amount of data transferred, the referring page and your browser identifier (user agent).

We process this data to operate the website securely and reliably, defend against attacks and find errors (legal basis: Art. 6(1)(f) GDPR, legitimate interest). We also evaluate it statistically without identifying individuals, for example to see which lessons are read. Log files are deleted automatically after no more than 60 days.

Hosting#

The website runs on a server operated by Hetzner Online GmbH, Industriestraße 25, 91710 Gunzenhausen, Germany, in a data centre in Finland (EU).

Local storage in your browser#

Your learning progress – completed lessons, exercise results for spaced review, flashcards, XP, streak, daily goal, badges – and settings such as colour scheme, sounds and step-by-step reading are kept in your browser’s local storage. This data never leaves your device and is not sent to us; there is no user account. A backup code is generated locally by your browser and is only shared if you copy it yourself. You can reset all data at any time on the “Progress” page or delete it in your browser settings.

User account (optional)#

You can learn without an account. If you choose to create one, we store on our server (see “Hosting”): your email address, your display name, your password only as a secure hash (bcrypt), language, registration and last login time, and your learning progress (the same data as in local storage). The legal basis is the performance of the user relationship (Art. 6(1)(b) GDPR).

While you are logged in, the site sets a strictly necessary session cookie (bmi_sid, only for addresses under /api/, valid for up to 180 days or until you log out). It is used solely for logging in, not for tracking; no consent is required for it.

To prevent abuse (too many login attempts, automated sign-ups) we store IP addresses or identifiers of login and registration attempts for at most 24 hours (Art. 6(1)(f) GDPR).

If you join the weekly leaderboard – optional and switchable off at any time – other learners see your display name and your XP for the current week. Your email address is never shown.

We send password reset emails only when you request them, using the email service Brevo (Sendinblue SAS, Paris, France) as a processor; only your email address, display name and the content of the email are transmitted. We send no advertising or newsletters.

On the “Account” page you can download all stored data and delete your account permanently at any time; this also deletes your saved progress and all sessions.

Accounts from the previous site: accounts created on butterflymarketinsider.com before the relaunch in October 2026 were carried over with email address, username, display name, registration date and password hash so that you can keep logging in. No other data from the old site was transferred. If you don’t want this, delete your account on the “Account” page or write to us.

External links#

In the news section we link to articles from external media. Only when you click such a link do you leave our website; the operators of the target sites are responsible for their data processing.

Contact by email#

If you email us, we process your details solely to answer your request (Art. 6(1)(b) or (f) GDPR) and delete them once they are no longer needed for that purpose.

Your rights#

You have the right of access, rectification, erasure, restriction of processing, data portability and objection. Contact us at the email address above. You also have the right to lodge a complaint with a data protection supervisory authority, in Austria the Datenschutzbehörde (www.dsb.gv.at).

As of October 2026