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Bluetooth scan works without turning on the bluetooth android

I am creating an application with Bluetooth Low energy. There is one interesting thing that I found out. I know that for API level 23 or higher you need to provide location permissions in addition to bluetooth for scanning to work. But I did not know that you can scan devices even if Bluetooth is disconnected from the settings. I have bluetooth turned off (but the location was still turned on), but I could still see the devices with the scan result.

Is this a bug in android where android uses bluetooth without suspecting it? or is it documented somewhere that I could not find.

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No. This is completely normal. In Android M, they configured permissions / added this feature to use Bluetooth for location. To do this, you only need a phone to listen to other BT devices. He does not need to broadcast himself. This is a much smaller privacy issue as you do not experience leaking your presence on other BT devices.

Read more about it here Android Police

I agree that the user’s description looks strange: "... scanning for Bluetooth devices, even when Bluetooth is turned off." Obviously, the BT antenna is not completely off. It should listen to other BT devices. But at the software level, the BT stack does not transmit its own address.

It is not clear how much this saves battery life since the BT antenna is still on.

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Source: https://habr.com/ru/post/1276043/

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