What is a MAC address?
A MAC address (Media Access Control address) is a 48-bit hardware identifier assigned to a network interface — every WiFi card, Ethernet port, and Bluetooth radio has one, usually written as six pairs of hex digits like F4:F5:E8:11:22:33.
Unlike an IP address, which changes depending on what network you're connected to, a MAC address is (normally) fixed to the physical hardware — it's set at the factory and doesn't change when you move between networks. It operates at a lower layer of networking than IP: your router uses MAC addresses to deliver traffic to the right device on your local network, before IP addressing even comes into play.
The address has two halves: the first 3 bytes are the OUI, identifying the manufacturer, and the last 3 bytes are a device-specific value the manufacturer assigns. That's why a MAC lookup can tell you "this device was made by Google" or "this is a Netgear device" — the manufacturer half is public information.
Modern phones complicate this: iOS, Android, and Windows 11 all rotate a randomized (private) MAC address by default per network, specifically so the real hardware address can't be used to track a device across locations. A randomized address looks the same format-wise but has no real manufacturer behind it.
FAQ
- Does a MAC address change?
- The hardware's factory-assigned MAC address doesn't change. But modern devices increasingly use a randomized MAC per network instead of broadcasting the real one — so what you SEE on your router can change even though the underlying hardware address hasn't.
- Can I change my MAC address?
- Yes — most operating systems let you manually override the MAC address a network interface presents (sometimes called MAC spoofing). This is different from automatic randomization, which is a built-in privacy feature.
- MAC address vs IP address — what's the difference?
- A MAC address identifies the physical hardware and is used for local-network delivery. An IP address identifies where a device is on a network and is used for internet-wide routing. One device typically has a fixed-ish MAC address but a changing IP address, depending on the network.