A MAC address (Media Access Control address) is a unique identifier assigned to the network interface card (NIC) of a device. It is used for communication within a local network. They operate at the Data Link Layer (Layer 2) of the OSI model.

A MAC address is an 48-bit value expressed in hexadecimal and divided into six pairs, separated by colons or hyphens (e.g. FF:00:FF:FF:00:FF). The first half of the address is the Organizationally Unique Identifier (OUI): It identifies the manufacturer. The second half uniquely identifies the device.

Although MAC addresses are static by default and hard-coded into hardware during manufacturing, they can be temporarily modified through software tools.

MAC addresses are important for local communication. When data is transmitted over a network, both the source and destination MAC addresses are embedded in the data frames. Devices such as switches for example use these addresses to forward data to the right port. Unlike IP addresses, which are also used for communication over the internet, MAC addresses are only used in local networks and are not used for routing data beyond it.