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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.