Last updated: 29 October 2026
This describes what LockDuck ("the app") collects and what it does not. We do not describe anything the app does not actually do.
| What | Your device's approximate latitude and longitude, via Android's ACCESS_COARSE_LOCATION permission |
|---|---|
| How | We use the last known location from cell towers or Wi-Fi, and request a fresh one only if none exists. We never request continuous updates |
| Why | To show the weather where you are |
| Where it is kept | On your device only. The last coordinate is saved in app storage so the next lookup is fast |
| If you decline | Seoul's weather is shown instead. The app still works |
Fetching a forecast means telling our server roughly where you are. But
the app folds your coordinates into a grid cell before sending them.
What actually leaves the device is a single cell name (for example
wydm6k) — your latitude and longitude never leave the device.
One cell is about 1.2 km across and 0.6 km tall.
The server looks up the forecast for that cell and caches it as
cell name + forecast publication time, shared by everyone in that cell.
Our server does not retain who was where.
The same holds outside Korea. The Korean forecaster covers only the Korean peninsula, so elsewhere we use forecasts from WeatherAPI.com. There too the app sends only the cell name, and our server asks WeatherAPI using that cell's centre point — your own coordinates are not passed on.
This used to work differently: the app called Open-Meteo directly and sent coordinates without folding them. That path was removed in October 2026 when the lookup moved to our server. The released app offers no way to select Open-Meteo.
We use Google Firebase Analytics to collect:
These records contain no name, email, phone number, or precise location. We have an automated check in our codebase that rejects any event field that could identify a person.
There is one reason we collect this: lock screen apps are routinely killed by manufacturer battery optimisation, silently. We cannot fix what we cannot see.
There is a banner ad at the bottom of the lock screen. We use Google AdMob. The ad is loaded only while the lock screen is showing. No other screen in the app carries advertising.
Serving that ad collects an Advertising ID. Google receives it. It never reaches our server — all our server receives is the grid coordinate used to look up the forecast (§1).
The ad slot never exceeds 20% of the screen height. We keep an empty gap between it and the unlock hint and shortcuts, so that reaching to unlock does not land on the ad.
Correction, 16 September 2026. This section used to say "the current version contains no advertising" and "we will update this page and notify you inside the app before that happens." The banner shipped first and this page followed late. We are leaving the record here rather than deleting it.
| Google Firebase Analytics | Diagnostics · policy |
|---|---|
| Google AdMob | Lock screen banner ads · Advertising ID · policy |
| Korea Meteorological Administration | Forecasts · queried by grid cell only |
| WeatherAPI.com | Forecasts outside Korea · queried by grid cell centre only · policy |
| Korea Environment Corporation (AirKorea) | Air quality grades · queried by province only |
| Amazon Web Services | Server and cache hosting (Seoul region) |
This app is not directed at children, and we do not collect information that would tell us whether a user is a child.
See the support page.
If this policy changes we update the date above. Changes that add to what we collect will also be announced inside the app.