Arrow sign on macOS Menu bar What is this arrow mark on the Menu bar? I am using macOS 10.12.4.
It shows up for few seconds and disappears automatically.
What you're seeing is the Location Services indicator.

This will appear whenever an app is currently using Location Services.  

It's not just an indicator, you can also click it to see which apps are using Location Services. 

For more information refer to About Location Services.