Privacy Policy
Last updated: 2026-06-19 · Information pursuant to Art. 13 GDPR.
We take the protection of your personal data seriously. HydroCalc is designed to collect as little data as possible. We do not use tracking, analytics, advertising, or non-essential cookies. All data is processed on servers located in the European Union.
1. Controller
The controller responsible for data processing is the service provider named in our Imprint. For any privacy request, contact: [your-email@example.com].
2. What data we process
a) When you use the calculator
The nutrient calculation runs entirely in your browser. Your inputs are not sent to us unless you choose to save a recipe (see below).
b) When you create an account
To register and sign in, we process your email address and an encrypted (hashed) password. This is handled by our authentication provider, Supabase.
c) Content you save
If you are signed in, the recipes, custom ingredients, target profiles, and water sources you choose to save are stored in your account.
d) Technical server logs
Our hosting and backend providers automatically process technical data required to deliver the service securely, such as your IP address, date and time of access, and the requested resource. These logs are used only for operation and security and are kept for a short period.
3. Purposes and legal bases
- Providing your account and saved content — to perform the service you request (Art. 6 (1)(b) GDPR).
- Security and stable operation (e.g. server logs) — our legitimate interest in a secure service (Art. 6 (1)(f) GDPR).
- Essential session storage — a strictly necessary token to keep you signed in (Art. 6 (1)(f) GDPR). No consent banner is required because no non-essential cookies are used.
4. Processors
We use the following processors under data processing agreements (Art. 28 GDPR), with data hosted in the EU:
- Supabase — authentication and database (EU region).
- Hostinger — website hosting (EU data centre).
We do not transfer your personal data to third countries outside the EU/EEA.
5. Storage period
Account data and saved content are stored until you delete them or close your account. Technical logs are deleted after a short retention period.
6. Your rights
Under the GDPR you have the right to:
- access your data (Art. 15);
- rectification (Art. 16);
- erasure (Art. 17);
- restriction of processing (Art. 18);
- data portability (Art. 20);
- object to processing (Art. 21);
- withdraw consent at any time (Art. 7 (3)).
You can export your data and delete your account yourself at any time in your account settings. You also have the right to lodge a complaint with a supervisory authority (Art. 77 GDPR), e.g. [your competent state data protection authority].
7. Children
This service is not directed at children under 16.
8. Donations and external links
Our footer contains an optional donation link to Ko-fi. Ko-fi is an external service with its own privacy policy. No data is shared with Ko-fi unless you choose to follow the link; any payment then happens entirely on Ko-fi's website, not here.
9. Changes to this policy
We may update this policy to reflect changes to the service or legal requirements. The current version always applies, with the date shown above.