Privacy Policy
This page explains which personal data hotmilk.ch processes, why, and what rights you have. It follows the Swiss Federal Act on Data Protection (FADP) and, where it applies, the EU General Data Protection Regulation (GDPR).
The hotmilk app for iOS and Android has a privacy policy of its own.
Last updated: October 2026
Controller and contact
Stephan Mathys
Switzerland
dive@hotmilk.ch
hotmilk.ch, the website and the app, is a private project. Write to the address above for any question about your data.
In short
- You can use the calculators without an account. hotmilk.ch itself then only keeps the server logs described below; on the calculator pages, Google shows advertising.
- hotmilk.ch uses no analytics and no social media plugins. Google may use cookies for personalised ads only with your consent.
- hotmilk.ch does not sell your data. With an account, the website shows no advertising.
Account and login
The website and the app use the same account. If you register, hotmilk.ch stores:
- your first and last name and your email address,
- your password, only as a salted hash,
- your dive organisation and level, if you enter them,
- what you save in your settings: tanks with their inspection dates, planner profiles and filling stations with their prices.
An administrator reviews every registration before the account becomes active. The data is used to run your account and the features you use with it (Art. 6(1)(b) GDPR). It is kept as long as your account exists.
You can delete your account yourself on the website, in your profile under Delete account, after confirming with your password. It is deleted at once together with everything you saved in it, on the website and in the app alike, and every login of the website and the app ends.
Cookies
When you log in, the website sets a session cookie. It keeps you logged in and protects the forms against cross-site request forgery. It is sent only over HTTPS and ends after 12 hours without activity or when you log out. The website cannot work without it, so it needs no consent.
Advertising with Google AdSense
The calculator pages show advertising from Google AdSense, a service of Google Ireland Limited, Gordon House, Barrow Street, Dublin 4, Ireland. The ads pay for the website and the app, which are free. Only visitors without an account see them: when you are logged in, or have ever logged in from this browser (see the account cookie), no ads are shown and the website loads no code from Google. Pages without ads, such as the login, the settings or this page, never load code from Google.
To show an ad, your browser loads it directly from Google. Google then receives your IP address, information about your browser and device, the address of the page and the time, and processes this data as a controller in its own right, under its privacy policy; how Google uses data from websites that show its ads is explained on How Google uses information from sites that use our services.
On your first visit, a consent message from Google asks whether Google may store cookies and similar identifiers in your browser and show you ads based on your interests. If you agree, Google may use them to personalise and measure ads (consent, Art. 6(1)(a) GDPR). If you do not agree, Google shows non-personalised or limited ads, chosen by the content of the page, which use cookies at most to limit how often an ad is shown and to detect fraud (legitimate interest in financing the website, Art. 6(1)(f) GDPR). You can change or withdraw your consent at any time through the link Privacy settings at the bottom of every page with ads; the withdrawal applies from then on. You can also manage the ads Google shows you in My Ad Center, or create a free account, which ends the advertising.
Mails
When you register, your details go by mail to the administrator, who approves or rejects the registration. You then get a mail with a link to set your password, or a mail with the reason for the rejection. You also get a mail when you reset your password. The mails go out through the mail service of Google Workspace (Google Ireland Limited and Google LLC, USA), which processes your email address and the content of the mail on behalf of hotmilk.ch.
Voluntary contributions through Stripe
Logged-in users can make a voluntary contribution. The payment takes place on a page of Stripe (Stripe Payments Europe, Ltd., Ireland). Stripe processes your payment details under its own privacy policy; hotmilk.ch never sees your card details.
hotmilk.ch stores the amount, the currency, the time, the status of the payment and the reference of the Stripe session, linked to your account. This data is used to process the contribution (Art. 6(1)(b) GDPR) and is kept as long as your account exists, or longer where the law requires it.
Hosting and server logs
The website and the interface the app talks to run on Amazon Lightsail of Amazon Web Services in Frankfurt, Germany. For every request the server logs your IP address, the date and time, the requested address, the response status, the referring page and the browser or app you use. The logs serve to operate the website and the app, to find errors and to defend against attacks (legitimate interest, Art. 6(1)(f) GDPR). They are deleted after 14 days at the latest.
Disclosure abroad
The data is stored in Germany, which offers an adequate level of data protection. Google, Stripe and Amazon Web Services are groups with headquarters in the USA, so data may be accessed from there. Where this is the case, the transfer is based on the EU-U.S. and Swiss-U.S. Data Privacy Framework or on the standard contractual clauses of the European Commission.
Your rights
You have the right to:
- know which data about you is stored,
- have wrong data corrected,
- have your data deleted,
- restrict or object to its processing,
- receive your data in a common electronic format.
Write to the address above. You can also lodge a complaint with the Federal Data Protection and Information Commissioner (FDPIC) or, in the EU, with the data protection authority of your country.
Changes
This policy changes when the website starts processing data in a new way. The date at the top shows the last change.