The MAC address for a system is its Media Access Control address, which is a unique string of hexadecimal characters that identifies your system’s physical port on the network. This address is used by routers on your local network to ensure proper assignment of IP addresses, and network information routing. It can also be used for special services like Wake On Lan, where you can send a datagram called a magic packet to a system to trigger it into an active mode from sleep or standby.

Because a MAC address is unique for a physical interface, your Mac may have several different MAC addresses. For instance, you will have one for your Wi-Fi adapter, and another for your Ethernet adapter. If you are configuring a router or other device that requires your MAC address, then you will need to differentiate between these to ensure proper communication with your device.

There are several ways to look up the MAC address in OS X:

The System Preferences

1. Open the Network system preferences
2. Select your desired network connection (usually the active one)
3. Click the Advanced button
4. Click the Hardware tab, where you will find the MAC address listed

The System Information Utility

1. Search for “System Information” in Spotlight and open the application (also in the Applications > Utilities folder)
2. Select the Network category
3. Select your Wi-Fi or Ethernet ports, and look up the respective MAC address

Note that you might see the MAC address listed for both Ethernet and Wi-Fi in the same pane, so be sure to differentiate between these by their labels.

The Terminal

1. Open the Terminal (in the Applications > Utilities folder)
2. Run the following command, replacing “Wi-Fi” with “Ethernet” (or “Ethernet 2”, etc.) where appropriate:

networksetup -getmacaddress Wi-Fi

Note that in this command, if the port exists then you will get a MAC address returned, but if not then you will get an error stating the parameters are invalid.