Unknown "white rectangle" system notification icon on Samsung Galaxy I have Samsung Galaxy S7 running on Android 7.0 Nougat. I got a new notification symbol that looks like a white rectangle on the right side (which is usually for system icons). 



Sometimes it's gone while I'm browsing with the Chrome browser but then it's back.

I don't use or install any Cast apps. Long-pressing the icon only open the notification bar, but no additional information. Toggling GPS, NFC, Bluetooth didn't help.

What does this icon represent?
Pull down the notification bar and long press on that notification, you should see the app associated with this icon. This could belong to an app you installed.