What is the function of the LED near the top left corner of Lumia 730?

[Windows Central Question]

First time in two years the LED light near the top left corner of my Lumia 730 started blinking today while I was connecting it with a USB cable as it was totally out of battery power (I didn't even know there was one until that happened ).

 

[milkyway]

Your LED is doing what the Windows home button is doing on phones with capacitive buttons. With Windows 10 there is support for notification LEDs but Microsoft is very quiet about actual support of this feature. There was a rumour some phones already have notification LEDs and they will get enabled with Windows 10, but that did not happen

 

[xandros9]

It has just about no function otherwise than what you see.

Windows 10 was supposed to support LEDs but nothing yet.

 

[f1saurabh]

I am on the latest stable build for non windows insider ( can't remember the build number) and the LED activates when you switch on the phone or restart it. To be able to see it in action you need to be in a dark room and focus on top left to the earpiece. Mind you that it comes on for literally for milliseconds so please be attentive. That's another use I guess.