Apple Remote Desktop Client 3.9.3 is an update for any Mac that is viewed or controlled from the Remote Desktop app. It's available as an automatic software update for the following versions of these operating systems:

macOS Sierra 10.12.2 or later

OS X El Capitan 10.11.6

OS X Yosemite 10.10.5

This update is recommended for all Apple Remote Desktop users. It addresses issues related to compatibility, reliability, and usability.