What is a MAC address?

A MAC address belongs to a network interface, not to the whole device. A laptop with Wi-Fi and an Ethernet port has two MAC addresses, one for each. You may also see it called a physical address, hardware address, Ethernet address or Wi-Fi address. They all mean the same thing.

MAC address meaning: what it is for

Data on a local network travels in chunks called frames. Every frame carries two MAC addresses: the device it is going to and the device it came from. A switch or Wi-Fi access point reads the destination address and sends the frame only towards that device. Without MAC addresses, every device on the network would have to receive everything and sort through it.

Think of it like a parcel and a building. The IP address is the street address that gets a parcel to the right building from anywhere in the world. The MAC address is the name on the parcel that gets it to the right person once it is inside. In networking terms, the MAC address works at the data link layer (layer 2 of the OSI model) and the IP address at the network layer (layer 3).

MAC address format and example

A MAC address is 48 bits, which is 6 bytes. Each byte is written as two hexadecimal (base 16) digits, so a full address is 12 digits. The digits run from 0 to 9 and then A to F, where A means 10 and F means 15. Any other letter, like G or Z, means it isn't a valid MAC address.

All three are the same address. Capital and small letters mean the same too, so f0 and F0 are equal. Here is that example converted to binary, one byte at a time. You can check any pair with our Number Base Converter.

Six bytes of 8 bits each makes 48 bits. With 48 bits there are 2⁴⁸ possible addresses, which is 281,474,976,710,656, or about 281 trillion.

Try it: this question shows you an address and asks whether it is a real MAC address or which pair breaks it.

MAC address lookup: what the first half tells you

A MAC address set at the factory has two halves. The first 24 bits (the first three pairs) are the OUI, the organisationally unique identifier, which the IEEE Registration Authority gives to a manufacturer. The manufacturer then chooses the last 24 bits for each device it makes, so no two of its devices should share an address. One OUI therefore covers 2²⁴ = 16,777,216 addresses.

That is how a MAC address vendor lookup works: it matches the first three pairs against the IEEE's public list. In the list downloaded on 7 November 2026, F0-D5-BF belongs to Intel Corporate and 00-00-0C to Cisco Systems. That list had 40,458 of these large blocks (called MA-L assignments). The IEEE charged a one off fee of US$3,585 for a publicly listed MA-L at the same date, and companies can pay extra to have their name hidden, so some lookups only say "Private".

The two special bits

Two bits in the first byte have special jobs, according to RFC 9542. They are the last two bits of the first byte in binary:

• The group bit (the very last bit, also called I/G): 0 means the address belongs to one device (unicast). 1 means it is for a group of devices (multicast or broadcast).
• The local bit (the second to last bit, also called U/L): 0 means a global address, set using a manufacturer's OUI. 1 means a locally administered address, made up by software rather than taken from the factory list.

In the example, F0 is 11110000 in binary. Both bits are 0, so it is a normal, factory style, single device address. Now take DA:4E:21:07:B3:5C. DA is 11011010: the group bit is 0 but the local bit is 1, so this is a locally administered address, the kind a phone makes up for privacy.

One group address is worth knowing: FF:FF:FF:FF:FF:FF, all 48 bits set to 1, is the broadcast address. A frame sent to it goes to every device on the local network.

How MAC addresses move data around a network

Switches learn where each address is

A switch keeps a MAC address table that pairs each address with one of its ports. Every time a frame arrives, the switch notes the sender's address and the port it came in on. Then it looks up the destination: if the address is in the table, the frame goes out of that one port. If it isn't, the switch sends the frame out of every other port, which is called flooding, and learns the right port when the reply comes back.

ARP: finding the MAC address for an IP address

Programs send data to IP addresses, but a frame on the local network needs a MAC address. The Address Resolution Protocol (ARP, set out in RFC 826) fills the gap for IPv4. Say your laptop wants to reach your printer at 192.168.1.40:

1. The laptop broadcasts a question to FF:FF:FF:FF:FF:FF: "Who has 192.168.1.40?"
2. Every device receives it, but only the printer answers: "192.168.1.40 is at" followed by its MAC address.
3. The laptop saves the answer in its ARP cache and sends its frames straight to the printer's MAC address.

Leaving the local network

To reach a website, your device sends the frame to your router's MAC address, with the website's IP address inside. The router takes the data out of the frame and puts it in a new frame for the next link, with new MAC addresses. This happens at every hop: the IP addresses travel end to end, but the MAC addresses change on each link. That is why a website never sees your device's MAC address.

MAC address vs IP address

You need both. The IP address gets data to the right network; the MAC address gets it to the right device on that network. The IP Addressing course covers the IP side, and the Networking Hardware course follows a frame through switches and routers step by step.

Random MAC addresses and private Wi-Fi addresses

A fixed MAC address is a privacy problem. Your phone sends it to every Wi-Fi network it joins, so anyone running those networks could spot the same device turning up in different places. Apple says this "allows a kind of user tracking or profiling".

So phones and laptops now make up a random MAC address for each network, with the local bit set to 1:

• iPhone and iPad: a different private Wi-Fi address for each network since iOS 14. From iOS 18 you can choose Off, Fixed or Rotating, and Rotating changes the address every 2 weeks. Apple makes Rotating the default on open or weakly secured networks.
• Android: since Android 10, a randomised address by default, kept the same for each network. Android 12 added addresses that can change each time you connect, for some networks.
• Windows: random hardware addresses can be turned on for all Wi-Fi networks or for one saved network, in Settings, Network and internet, Wi-Fi, if the Wi-Fi adapter supports it.

This can trip up home networks. If your router blocks unknown devices or gives a device a fixed IP address by its MAC address, a private address looks like a new device. You can turn the private address off for that one network instead of everywhere.

How to find your MAC address

Every device shows it somewhere. Remember that a device with private addresses has two: the hardware address and the private one it uses on each Wi-Fi network.

Can you change a MAC address?

The factory address is stored in the network hardware, but the operating system can tell the network card to use a different one. Private Wi-Fi addresses work exactly this way. Doing it by hand to pretend to be another device is called MAC spoofing. Because any address can be copied, MAC filtering on a router (letting in only listed addresses) is weak security on its own. A strong Wi-Fi password does far more.

Common mistakes

• Thinking it has anything to do with Apple Macs. MAC stands for media access control. Every networked device has one, whatever the brand.
• Thinking a device has only one. Each network interface has its own, and a phone may use a different private address on every Wi-Fi network.
• Mixing up the sizes. A MAC address is 48 bits, or 12 hex digits. An IPv4 address is 32 bits.
• Thinking websites can see it. MAC addresses stay on the local network. Each router puts new ones on the frame.
• Trusting a lookup too far. The OUI names the chip's maker, not the device's owner, and it means nothing for a private address.
• Calling it permanent. The factory address is fixed in hardware, but the address a device actually uses can be set by software.

Read next

Computer Science · NetworksWhat is an IP address? IPv4, IPv6 and how to find yoursWhat an IP address is and how it works: IPv4 and IPv6, public vs private, static vs dynamic, what your IP reveals and how to find yours.