A MAC (Media Access Control) address is a 48-bit hardware identifier assigned to a network interface, written as six pairs of hexadecimal digits such as 3C:22:FB:4A:91:0E. Devices use it to deliver data to each other on the same local network, while IP addresses handle routing between networks.
Every Wi-Fi card, Ethernet port and Bluetooth radio has one. Unlike your IP address, your MAC address never leaves your local network, but it still matters for router settings, troubleshooting and privacy.
MAC address format
A MAC address is 48 bits, or 6 bytes (often called octets). Each octet is written as two hexadecimal digits, so the whole address is 12 hex digits. The same address can be written in several styles depending on the operating system or vendor:
| Style | Example | Where you see it |
|---|---|---|
| Colon-separated | 3c:22:fb:4a:91:0e | macOS, Linux, iOS, Android |
| Hyphen-separated | 3C-22-FB-4A-91-0E | Windows |
| Dotted groups of four | 3c22.fb4a.910e | Cisco equipment |
| Bare | 3C22FB4A910E | Some databases and router exports |
Upper- or lowercase letters make no difference. The IEEE now formally calls these identifiers EUI-48; "MAC-48" is an older name for the same thing.
The OUI: identifying the manufacturer
A traditional, factory-assigned MAC address has two parts:
- OUI (Organizationally Unique Identifier): the first 24 bits, or first three octets (
3C:22:FBin the example). Manufacturers buy OUIs from the IEEE Registration Authority, so the OUI tells you which company made the network interface. - Device-specific part: the last 24 bits (
4A:91:0E), which the manufacturer assigns uniquely to each interface it produces.
Because 24 bits allows about 16.7 million combinations per OUI, large vendors hold many OUIs. The IEEE also issues smaller blocks, MA-M (28-bit prefix) and MA-S (36-bit prefix), to organizations that need fewer addresses. You can identify the vendor behind any address with our MAC address lookup, which is useful for working out what an unknown device on your network is.
The two special bits in the first octet
The two lowest bits of the first octet carry meaning. Write the first octet in binary to see them; for 3C that is 00111100.
Unicast or multicast (I/G bit)
The least significant bit of the first octet is the Individual/Group bit. If it is 0, the address belongs to one interface (unicast). If it is 1, it is a multicast address that many interfaces can listen to. The broadcast address FF:FF:FF:FF:FF:FF, used to reach every device on a network segment, has every bit set.
Global or locally administered (U/L bit)
The second-least-significant bit is the Universal/Local bit. If it is 0, the address is universally administered, meaning it comes from an IEEE-assigned OUI. If it is 1, the address is locally administered: it was set by software or an administrator, not burned in by the manufacturer. Randomized Wi-Fi addresses, virtual machines and many containers use locally administered addresses.
A quick rule of thumb: a unicast address is locally administered if its second hex digit is 2, 6, A or E. For example, 02:00:5e:10:00:01 and a6:83:e7:2b:4c:19 are locally administered, while 3c:22:fb:4a:91:0e is not. Locally administered addresses will not match a vendor in an OUI lookup.
MAC address vs IP address
| MAC address | IP address | |
|---|---|---|
| Network layer | Layer 2 (data link) | Layer 3 (network) |
| Length | 48 bits | 32 bits (IPv4) or 128 bits (IPv6) |
| Assigned by | Manufacturer or the device's OS | Your router (local) or ISP (public) |
| Scope | Only the local network segment | Routed across the internet |
| Visible to websites | No | Yes, your public IP |
The two work together. When your laptop sends a packet to another device on the same network, it needs that device's MAC address. IPv4 uses ARP (Address Resolution Protocol) to ask "who has 192.168.1.1?", and IPv6 uses Neighbor Discovery for the same job. For anything outside your network, your device sends the frame to your router's MAC address, and each router along the way rewrites the MAC header for the next hop while the IP addresses stay the same. That is why websites cannot see your MAC address; they only see your IP address.
You can see your device's ARP cache with arp -a on Windows, macOS and Linux, or ip neigh on Linux.
MAC addresses inside IPv6 addresses
Older IPv6 implementations built the second half of an address from the MAC using modified EUI-64: insert FF:FE in the middle of the MAC and flip the U/L bit. The MAC 3c:22:fb:4a:91:0e becomes the interface ID 3e22:fbff:fe4a:910e, giving an address like 2001:db8:1:2:3e22:fbff:fe4a:910e. Because that exposes a stable hardware identifier to every website, modern systems use random or stable-but-opaque identifiers instead. If you see ff:fe in the middle of an IPv6 address, it was probably derived from a MAC.
Randomized and private Wi-Fi addresses
Wi-Fi devices constantly broadcast their MAC address while searching for and joining networks, which made it possible for shops, venues and anyone with a scanner to track a phone over time. All major operating systems now use randomized, locally administered MAC addresses for Wi-Fi:
- iPhone and iPad: "Private Wi-Fi Address" is on by default since iOS 14, using a different address for each network. Recent versions let you choose Off, Fixed or Rotating per network under Settings > Wi-Fi > (i).
- Android: since Android 10, randomized MAC is the default for each saved network. Change it under the network's settings, in an option usually labeled "Privacy" with "Use randomized MAC" or "Use device MAC".
- Windows 10 and 11: "Random hardware addresses" can be turned on globally under Settings > Network & internet > Wi-Fi, and per network with options such as On, Off or Change daily.
- macOS: recent versions offer a Private Wi-Fi Address option per network in the network's Details in System Settings.
Randomization is good for privacy but can confuse home networks. A device may appear as "new" in your router, lose its DHCP reservation, or be blocked by a MAC allowlist. For trusted networks where you need a stable identity, set the private address to Fixed or turn it off for that network only.
How to find your MAC address
Windows
Open Command Prompt and run ipconfig /all. Look for Physical Address under the adapter you use. getmac /v lists all adapters in a compact table. In Settings, open Network & internet, select Wi-Fi or Ethernet, then Hardware properties.
macOS
In Terminal, run ifconfig en0 | grep ether (en0 is usually Wi-Fi on laptops). Or go to System Settings > Wi-Fi, click Details next to your network, and read the Wi-Fi address. With Private Wi-Fi Address on, this shows the address in use on that network.
Linux
Run ip link show. The address follows link/ether for each interface.
iPhone and iPad
Settings > Wi-Fi, tap (i) next to the network to see the address used there. Settings > General > About shows the hardware Wi-Fi address.
Android
Settings > Network & internet > Wi-Fi, tap the connected network for the address used on it. Settings > About phone shows the device MAC. Exact menu names vary by manufacturer.
Your router
The router's client or DHCP list shows the MAC, IP and name of every connected device. Our guide to router login addresses explains how to reach that page.
Frequently asked questions
Can someone track me by my MAC address?
Not over the internet, because your MAC never leaves your local network. Nearby Wi-Fi scanners could historically track devices by MAC, which is why phones and computers now randomize it.
Can two devices have the same MAC address?
They should not on the same network, but duplicates do happen, through manufacturing errors, cloned virtual machines or deliberate spoofing. A duplicate on the same segment causes intermittent connectivity for both devices.
Can I change my MAC address?
Yes. Most operating systems let you set a locally administered address in the network adapter settings, and Wi-Fi randomization does it automatically. The burned-in hardware address remains unchanged.
Why does my MAC lookup say "unknown vendor"?
The address is most likely locally administered, such as a randomized Wi-Fi address, so it does not contain a registered OUI. Check whether the second hex digit is 2, 6, A or E.