Privacy
Saved places stay on your computer.
This website
It has no analytics, advertising trackers or email collection. It never asks for your location or connects to your iPhone. The hosting provider receives normal web requests.
The desktop app
Saved places, recent locations, routes and recovery state stay on your computer. The device library saves pairing records and developer files on your computer too.
Map tiles come from Esri, with OpenStreetMap as a fallback. Searches use Photon, and road routing uses Valhalla through FOSSGIS. Those providers receive the area, search or route points they need.
Location changes
Only the controls you choose in the app send a simulated location. Other apps may detect or refuse it. Restore real GPS asks the iPhone to reset, so check the result in Maps.