Privacy Policy
Last updated: September 6, 2026
1. Privacy at a Glance
As a rule, this website can be used without registration and without providing a name or contact details. We follow the principle of data minimisation and currently use neither a web analytics service nor user tracking.
When the website is accessed, technically necessary connection data is generated by the hosting provider. Settings such as language and appearance are stored exclusively in the browser. The book application delivers its essential fonts, scripts, and libraries locally. The exceptions that currently apply to individual interactive tools are described below.
2. Controller
The controller responsible for processing personal data on this website is identified in the legal notice.
3. Hosting and Server Logs
This website is hosted by:
STRATO AG
Otto-Ostrowski-Straße 7
10249 Berlin
Germany
When a page is accessed, the browser necessarily transmits technical information, in particular the IP address, the requested address, the date and time of the request, and browser information. The hosting provider may process this data in server logs in order to deliver the website, identify errors, and defend against attacks. According to information provided by STRATO, the hostname or IP address is anonymised in the access logs made available to customers.
We do not combine this log data with other data sources. Processing serves the secure and technically reliable delivery of the website and is based on Article 6(1)(f) GDPR. The specific retention period for technical logs depends on the settings and conditions of the hosting package.
4. Cookies and Local Browser Storage
Public Reading Area
We do not use cookies for normal use of the public book. The website uses local browser storage (localStorage) to save settings selected by the user:
- selected language (
app-locale) - selected colour scheme (
app-theme) - selected page transition (
app-page-transition)
This information remains stored on the device until it is deleted in the browser settings. It is not used to create profiles and is not automatically transmitted to the server with HTTP requests.
When an interactive tool is opened, its launch parameters may temporarily be stored in session storage (sessionStorage). They are used solely to open the tool with the settings selected on the book page and are discarded by the browser no later than the end of the browser session.
Protected Editorial Area
A technically necessary, time-limited authentication cookie is set only after a user signs in to the non-public editorial area. It is marked HttpOnly and SameSite=Lax and is used exclusively to secure the editorial session. Regular readers do not receive this cookie.
5. Interactive Tools and External Connections
The interactive tools are generally delivered together with the book and run predominantly in the browser. At present, however, six tool builds load the MathJax formula library from jsDelivr (cdn.jsdelivr.net) when opened. This establishes a direct connection to the CDN provider's servers. For technical reasons, information including the IP address, browser information, the requested file, the date and time, and limited referrer information is transmitted. jsDelivr states that it does not use cookies for its CDN service. Further information is available in the jsDelivr Privacy Policy.
At the user's express request, individual tools may also retrieve datasets or other content from an external source. In this case, a connection is established with the provider identified for that source. Apart from this, input and calculations in the tools are generally processed in the browser.
The external MathJax integrations are to be replaced by local delivery. Until this change has been completed, the preceding description reflects the current state.
6. External Links
This website contains links to external services, for example to further sources or the mailing list. A connection to those providers is established only when such a link is clicked. The operator of the website subsequently visited is responsible for the processing of data there.
7. Encrypted Transmission
The publicly available website uses SSL or TLS encryption. An encrypted connection can be identified by https:// in the browser's address bar.
8. Data Subject Rights
Subject to the applicable statutory requirements, data subjects have rights including access, rectification, erasure, restriction of processing, data portability, and objection. They also have the right to lodge a complaint with a data protection supervisory authority.
Settings stored locally in the browser can be deleted at any time using the browser's functions; we do not have access to this data. If you have questions about the processing of personal data, you can contact us using the details provided in the legal notice.