What is geofencing

Definition

What is geofencing?

A geofence is a virtual boundary around a geographic area, used to permit or deny an action depending on whether a device is inside it.

Where it came from

Geofencing started in logistics and marketing. A fleet system alerts a dispatcher when a truck leaves a depot. A retail app sends a coupon when a phone comes near a store. In both cases, being slightly wrong is cheap.

The same idea now carries legal weight. A wager is lawful inside a state line and unlawful outside it. A trade is allowed from one country and sanctioned from another. Where a mistake breaks the law, a geofence needs a stricter test.

The shape of the boundary

A radius around a point, which is simple and enough for a store or a depot.
A polygon, which follows a real boundary: a state line, a reservation, a casino floor.
A set of cells, such as an H3 grid, which makes large or irregular areas cheap to test.
A named region, such as a country or U.S. state, maintained by someone else.

An IP blocklist is not a geofence

Blocking traffic from a country’s IP ranges is often called geofencing. It is an approximation: it tests where the traffic entered the network, not where the device is. That is good enough to enforce most video licences. It is not good enough where the boundary is a legal line. See IP geolocation vs device geolocation.

The location signal that tests a geofence sets how strict it can be.

You can try a device-based geofence in a browser at geofencing.octetproof.com.