> For the complete documentation index, see [llms.txt](https://docs.sendstackhq.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.sendstackhq.com/live-tracking-apis/geofences.md).

# Geofences

**Geofences** are designated geographic areas that you can define. Once created, these areas can trigger **geofence entry ("geofence in")** and **geofence exit ("geofence out")** events. When a tracker enters or exits the defined area, the corresponding event is emitted.

Our API uses the **POLYGON** method to define geofences. You must ensure that the polygon coordinates accurately map to the intended area during creation.

**Example of a polygon geofence:**

```
POLYGON ((6.57955384860341 3.428432957806109, 6.4082822454249 3.44384423420928, 6.421780818038414 3.5975749615640495, 6.574921615748536 3.6404239396161984, 6.57955384860341 3.428432957806109))
```

Geofences can also be updated after creation.