What this is
Lüften is a free app that recommends when to open and close your windows for passive cooling. This policy describes what limited information the app uses to do that.
No account
Lüften has no sign-up, login, or user profile. The app generates a random anonymous identifier the first time you open it and stores it on your device. It is never linked to your name, email, or any account.
What's sent to our servers
- Your approximate location (latitude / longitude), used to fetch the local weather forecast.
- Your language preference, used to deliver notifications in your language.
- Your anonymous device identifier, used so the server can match a forecast lookup to your device.
That's the complete list.
Anonymous usage analytics
The app sends a small number of named events to understand how it is used — for example, whether notifications are enabled or whether a user deletes their data. Events are tied only to your anonymous device identifier, never to any personal information.
Analytics are processed by PostHog (EU region). PostHog is configured without session recording, without autocapture, and without IP address collection. No advertising networks or data brokers receive this data.
What we don't collect
No name, email, phone, contacts, photos, IP-address logging beyond what the host needs to route a request, advertising identifiers, screen recordings, cross-app tracking, crash reports tied to identity, or third-party tracking SDKs.
Where the data goes
Forecast lookups call the weather provider (WeatherAPI.com) with your coordinates. Your device row is stored in our backend (Supabase, hosted in the EU). Anonymous usage events are sent to PostHog (EU region). Notifications are scheduled on your device, not sent from our servers.
How long we keep it
Your device row persists until you delete it from inside the app (Settings → Delete my data) or stop using the app for an extended period. Deleting from the app removes the row from the backend. Anonymous usage events are retained for 12 months.
Children
The app is rated 4+ but is not directed at children and does not knowingly collect data from anyone.
Changes
If this policy changes, the "Last updated" date at the top of this page will move.
Contact
Privacy questions: support@luften.app.