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Proximity Events Specification: How To Receive Events From Device Proximity Sensors

by Mozilla ContributorsJune 10th, 2020

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Proximity events are a handy way to know when a user is close to a device. These events make it possible to react to such a change, for example by shutting down the screen of a smartphone when the user is having a phone call with the device close to their ear. The API requires the device to have a proximity sensor, which are mostly available only on mobile devices. This is an experimental technology. Check the Browser compatibility table carefully before using this in production before using it in production.

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This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The proximity events are a handy way to know when a user is close to a device. These events make it possible to react to such a change, for example by shutting down the screen of a smartphone when the user is having a phone call with the device close to their ear.

Note: Obviously, the API requires the device to have a proximity sensor, which are mostly available only on mobile devices. Devices without such a sensor may support those events but will never fire them.

Proximity Events

When the device proximity sensor detects a change between the device and an object, it notifies the browser of that change. When the browser
gets such a notification, it fires a

DeviceProximityEvent

for any change, and a

UserProximityEvent

event in the case of a more rough change.

This event can be captured at the

window

object level by using the

addEventListener

method (using the

deviceproximity

userproximity

event name) or by attaching an event handler to the

window.ondeviceproximity

window.onuserproximity

properties.

Once captured, the event object gives access to different kinds of information:

The
```
DeviceProximityEvent
```
event provides an exact match for the distance between the device and the object through its
```
value
```
property. It also provides the closest and farthest distance the device is able to detect something through its
```
min
```
and
```
max
```
properties.
The
```
UserProximityEvent
```
event provides a rough approximation of the distance, expressed through a boolean. The
```
UserProximityEvent.near
```
property is
```
true
```
if the object is close or
```
false
```
if the object is far.

Example

window.addEventListener('userproximity', function(event) {
  if (event.near) {
    // let's power off the screen
    navigator.mozPower.screenEnabled = false;
  } else {
    // Otherwise, let's power on the screen
    navigator.mozPower.screenEnabled = true;
  }
});