What is Exit alert?

An exit alert fires when a device crosses from inside a geofenced zone to outside it. It is the most-used notification in geofencing, because the questions people actually have are usually about departure: did the car leave the depot, did the child leave school grounds, did the trailer leave the yard.

Exit versus enter

Both directions can be monitored, and they answer different questions.

	Fires when	Typical question
Exit alert	Device leaves the zone	”Did something leave that should have stayed?”
Enter alert	Device arrives in the zone	”Did something arrive that I was waiting for?”

Exit alerts dominate in safety and asset-protection use cases, where the zone represents somewhere the device is supposed to remain. Enter alerts suit logistics — a delivery reaching a customer, a vehicle arriving on site.

They are not symmetric in difficulty. An enter alert that fires slightly late is mildly annoying. An exit alert that fires late may be the one that mattered, and an exit alert that fires falsely twenty times trains the recipient to ignore it.

The time dimension

A raw exit alert — fire whenever the boundary is crossed — is usually wrong, because departures are only interesting during certain periods.

A child leaving school grounds at 11:00 is worth knowing about. The same child leaving at 16:30, when school ends, is not. A geofence with no sense of time sends both, and the second kind trains people to dismiss the first.

Geoblip attaches an active window to each device-zone pairing: specific days and a start and end time. Positions arriving outside that window are still recorded, and the device’s inside/outside state is still tracked correctly — but no alert is sent. The same physical zone can be monitored 08:30–16:30 on weekdays for one device and never for another.

Duplicate suppression

The naive implementation alerts on every observed inside-to-outside transition. Because GPS drift scatters reported positions by tens of metres, a stationary device near a boundary produces many such transitions, and the user gets a stream of alerts from something that never moved.

Geoblip sends an exit alert only on the transition of the pairing’s status from ok to alerting. Once that alert is open, further apparent exits update the physical position but send nothing. A second exit alert requires the device to genuinely return to the zone first — completing an alerting → ok → alerting cycle. See alert debouncing for the full state table.

What happens after

An exit alert is not the end of the sequence. The alert stays open until one of two things resolves it:

• The device returns — a recovery alert is sent and the original exit alert is stamped as resolved.
• The monitoring window closes with the device still outside — a distinct schedule-end notification is sent, and the status resets so the next window starts clean.

Without one of these, an alert would sit open forever and the next genuine exit would be suppressed. Closing the loop is what makes the alert stream readable rather than a list of unresolved incidents.

Where exit alerts are used

• School hours — a child leaving the campus during lesson time
• Dementia and elderly care — someone leaving a safe area, particularly at night
• Fleet — a vehicle leaving the depot outside working hours
• Equipment — a generator or trailer leaving a site
• Pets — a dog leaving the garden

The common thread is that the zone represents where the device is meant to be, and departure is the exception worth interrupting someone for. See geofencing for how the pieces fit together, or how Geoblip works for the setup.

Last reviewed 7 August 2026.