Privacy policy.

1. Controller

Sergey Kasatov
Cologne, Germany (postal address on request)
Email: sergey@kasatov.de

2. What this site does not do

kasatov.de is a static website. It sets no cookies, embeds no third-party content (no videos, maps, social buttons or external fonts), and loads its fonts from its own server. It does not build profiles and does not pass data to advertisers. The only external request your browser makes is to the analytics service described in section 4.

3. Hosting and server logs

The site is delivered by GitHub Pages, a service of GitHub, Inc., 88 Colin P. Kelly Jr. Street, San Francisco, CA 94107, USA. When you open a page, GitHub's servers receive the data that every web request carries: your IP address, the page requested, date and time, the referring page, and your browser and operating system. GitHub states that it logs visitor IP addresses for GitHub Pages sites to comply with legal obligations and to keep the service secure; see the GitHub General Privacy Statement. GitHub states that it participates in the EU-U.S. Data Privacy Framework for transfers to the USA.

Legal basis: my legitimate interest in a securely and reliably delivered website (Art. 6(1)(f) GDPR). I have no access to these logs beyond what GitHub provides.

4. Visitor statistics (GoatCounter)

To see roughly how many people read which pages, this site uses GoatCounter, an open-source, privacy-focused analytics service. When a page loads, your browser sends one request to gc.zgo.at with the page address, the referring site, your screen size and your browser's User-Agent string; the country and region are derived from your IP address. GoatCounter sets no cookies and does not store your IP address; to count a visit only once it keeps a short-lived hash that cannot be traced back to you. Details: GoatCounter privacy policy and GoatCounter GDPR notes.

Legal basis: my legitimate interest in understanding whether the site is found and read (Art. 6(1)(f) GDPR). If you block the request in your browser, the site works exactly the same.

5. Contact by email

If you write to me, I process the data you send (your email address, name, and the content of the message) to answer you. Where the contact concerns a possible employment or engagement, the legal basis is Art. 6(1)(b) GDPR (steps prior to a contract); otherwise it is my legitimate interest in answering enquiries (Art. 6(1)(f) GDPR). I keep the correspondence as long as the conversation requires and as long as I may need to document it, and delete it on request.

6. Local storage

If you switch the site between the paper and blueprint theme, your choice is stored in your browser's local storage (key theme) so the site remembers it on the next visit. This value never leaves your browser and is not a cookie.

7. External links

This site links to LinkedIn, GitHub, Tableau Public, Streamlit Community Cloud, Credly, Udemy, LinkedIn Learning and Analyst Builder. No data is transferred to these services while you read this site; their own privacy policies apply once you follow a link.

8. Your rights

Under the GDPR you have the right to access the personal data I hold about you (Art. 15), to have it rectified (Art. 16) or erased (Art. 17), to restrict its processing (Art. 18), to receive it in a portable format (Art. 20), and to object to processing based on legitimate interest (Art. 21). To exercise any of these rights, write to sergey@kasatov.de. You also have the right to lodge a complaint with a data-protection supervisory authority; for me that is the Landesbeauftragte für Datenschutz und Informationsfreiheit Nordrhein-Westfalen (ldi.nrw.de).

9. Changes

I update this policy when the site changes, for example if a new service is added. The current version always applies.

Last updated: 3 September 2026 · Legal notice