DAX Practice

Privacy policy

In short

  • The first three lessons work without an account. Your progress is then kept only in your browser.
  • From lesson 4 you need a free account: your email address, or Google sign-in. No name, username or password.
  • To buy Pro you pay through Stripe. We never see your card details.
  • We count visits with our own cookieless statistics. No Google Analytics, no tracking cookies, no advertising, no consent banner needed.

Controller

Sascha Heyer, hello@daxpractice.com. Further details are in the legal notice.

Hosting and server logs

The site and its API run on Google Cloud Run (Google Cloud EMEA Limited, Dublin, Ireland) in the europe-west1 region (Belgium). Each request is logged with the IP address, time, requested address, browser (user agent) and response status, to keep the service running and secure. The logs are stored in Google Cloud Logging and deleted after 30 days. Legal basis: Art. 6(1)(f) GDPR, our legitimate interest in a secure, working service.

Learning progress in your browser

Your checked lessons, your formulas, the days on which you checked a lesson and a few settings (for example the address a sign-in link was sent to, until you open it) are stored in your browser’s local storage. Nothing of this leaves your device until you sign in. We set no cookies. This storage is strictly necessary for the service you request (§ 25(2) no. 2 TDDDG). You can delete it in your browser at any time.

Your account

Sign-in uses Firebase Authentication (Google Ireland Limited, Dublin, Ireland). It stores your email address, a user ID and the times of sign-up and sign-in. If you use Google sign-in, Google also passes your name and profile photo, which Firebase stores with the account; we only use the name in the account menu if there is no email address.

With your account, we store in Cloud Firestore (Google, europe-west1, Belgium):

  • your learning progress: checked lessons, your formulas, attempts and completion dates, and the days on which you checked a lesson (your streak and points are calculated from these);
  • if you buy Pro: your plan, its status, the end of the current period, and the Stripe customer and subscription IDs;
  • a log of the transactional emails we sent you (address, type and time), so that no email goes out twice.

Legal basis: Art. 6(1)(b) GDPR, providing the service you signed up for. We keep the data until you delete your account. You can do that yourself under Account, Delete account: it deletes your sign-in, your progress, your Pro status and the email log. A running subscription has to be cancelled first.

Emails

We only send emails that belong to your account or a purchase: sign-in links you ask for, one welcome email when you create an account, and confirmations of a purchase, a cancellation or a failed payment. No newsletters and no tracking pixels. They are sent through Resend (Plus Five Five, Inc., San Francisco, USA) from its EU sending region. Resend processes your email address and the content of the email. Legal basis: Art. 6(1)(b) GDPR. Resend is certified under the EU-U.S. Data Privacy Framework, and its data processing agreement includes the EU standard contractual clauses.

Team inquiries

If you use the form on the teams page, we receive your name, company, email address, team size and message by email at hello@daxpractice.com, sent through Resend as described above, and Resend sends you one confirmation. We don’t store the inquiry anywhere else and use it only to answer you and, if you buy, to prepare the quote and invoice. Legal basis: Art. 6(1)(b) GDPR, steps you ask for before a contract. We delete the inquiry when it is no longer needed for that, unless tax or commercial law requires us to keep it.

Payments

Pro is paid through Stripe (Stripe Payments Europe, Ltd., 1 Grand Canal Street Lower, Dublin 2, Ireland). Stripe collects your payment details and billing address directly; we never see your card number. We receive and store your plan, the status of your subscription or Lifetime purchase, the end of the current period and the Stripe customer ID. Invoices are kept by Stripe for as long as tax and commercial law require. Legal basis: Art. 6(1)(b) and (c) GDPR.

Our own visitor statistics

When you arrive on the site, a small script (visit.js) sends one record to our statistics service on Google Cloud: the page you entered on, the referring page without its parameters, campaign tags in the link, your time zone and your browser language. The service derives the device type, browser and operating system from the user agent, and a country from the time zone. To count unique visitors it forms a hash from your IP address and user agent that changes every day; the IP address itself is not stored, and nothing is stored in your browser. The records are kept in Google BigQuery in the EU and deleted after 24 months. Legal basis: Art. 6(1)(f) GDPR, our legitimate interest in knowing how the site is found and used. You can object at any time by email.

What we don’t use

No Google Analytics, no advertising or social media trackers, no cookies. Fonts and scripts are served from this site. Sign-in and your account talk to Google’s Firebase services as described above, and Google’s own privacy policy applies inside the Google sign-in window.

Transfers outside the EU

Google, Stripe and Resend may process data in the United States. These transfers are based on the EU-U.S. Data Privacy Framework and on the EU standard contractual clauses.

Your rights

You have the right to access, rectify and erase your data, to restrict its processing, to data portability, and to object to processing based on our legitimate interests. Write to hello@daxpractice.com. You can also lodge a complaint with a data protection supervisory authority, in particular in the EU member state where you live.

Updated: November 2026