What Is a MAC Address?
A MAC (Media Access Control) address is a unique 48-bit identifier assigned to a network interface card (NIC) by its manufacturer. It is used at the data link layer (OSI Layer 2) to identify devices on a local network segment. Unlike an IP address, a MAC address is not routable across the internet and never leaves the local network. See the IP vs MAC address comparison for a side-by-side breakdown.
MAC Address Format and Structure
| Component | Bits | Description | Example |
|---|---|---|---|
| Full MAC Address | 48 bits (6 bytes) | Written as 6 hex octets separated by colons or hyphens | 00:1A:2B:3C:4D:5E |
| OUI (Organisationally Unique Identifier) | First 24 bits (3 bytes) | Assigned to manufacturers by IEEE - Identifies the vendor | 00:1A:2B = Intel, 3C:22:FB = Apple |
| NIC-specific portion | Last 24 bits (3 bytes) | Assigned by the manufacturer to uniquely identify the interface | 3C:4D:5E |
| Unicast/Multicast bit | Bit 0 of first byte | 0 = unicast (individual device); 1 = multicast (group) | 00 = unicast |
| Universal/Local bit | Bit 1 of first byte | 0 = globally unique (burned-in by manufacturer); 1 = locally administered (randomised or manually set) | 2 in second nibble = locally administered |
Burned-In vs Locally Administered MAC Addresses
The original MAC address burned into the NIC hardware by the manufacturer is globally unique. However, operating systems can override this with a locally administered address set in software - Commonly called MAC spoofing or MAC randomisation. When a MAC address is locally administered, the second-least-significant bit of the first byte is set to 1, which is how you can identify a randomised address.
MAC Randomisation for Privacy
- iOS 14+, Android 8+, and Windows 10 1903+ all randomise MAC addresses per Wi-Fi network by default to prevent tracking across access points.
- Wi-Fi access points and network analytics systems can track which MAC addresses visit a location and how frequently - MAC randomisation defeats this tracking at the hardware level.
- MAC randomisation generates a new pseudo-random locally administered MAC address each time your device connects to a new (or previously randomised) Wi-Fi network.
- Some enterprise networks use MAC address filtering as an access control - MAC randomisation can cause issues on these networks, requiring you to disable it for that specific network.
- Your MAC address is only visible within your local network - It is not transmitted in IP packets and is never seen by websites you visit. Websites instead see your public IP address.
How to Find Your MAC Address on Any Device
| Device | Where to Look |
|---|---|
| Windows | Settings → Network & internet → Wi-Fi → Hardware properties → "Physical address (MAC)" - Or run ipconfig /all and read "Physical Address" |
| macOS | System Settings → Wi-Fi → Details → Hardware - Or run ifconfig en0 | grep ether in Terminal |
| iPhone / iPad | Settings → General → About → Wi-Fi Address (per-network address shown under Settings → Wi-Fi → ⓘ when Private Wi-Fi Address is on) |
| Android | Settings → About phone → Status information → Wi-Fi MAC address - The per-network randomised MAC is under the network's gear icon → Privacy |
| Router / other devices | Usually printed on the device label, and listed per client in your router's admin page |
What MAC Addresses Are Used For in Practice
Delivery within the local network
Every frame on Ethernet or Wi-Fi is addressed by MAC. When your device wants to reach a local IP, ARP (Address Resolution Protocol) broadcasts "who has this IP?" and caches the answering MAC - Run arp -a to see your device's current table. Switches learn which MAC lives on which port and deliver frames only where needed. All of this happens below the IP layer, which is why the full journey of a packet swaps MAC addresses at every router while the IP addresses stay fixed - The division of labour explained in IP vs MAC address.
Network administration
Routers use MACs for DHCP reservations (always give this device the same IP - Handy alongside DHCP), for parental controls and per-device bandwidth rules, and for MAC filtering. Filtering deserves a caveat: because MACs are broadcast unencrypted in Wi-Fi frames and trivially spoofed, a MAC allowlist stops casual users only - A strong WPA2/WPA3 passphrase is the real access control, as covered in securing your home router.
What This Means for You
For everyday privacy, the single setting worth checking is MAC randomisation - On for networks you do not control (cafés, airports, hotels), so venues cannot recognise your device across visits, and off (or "fixed") for your home network if your router uses DHCP reservations or MAC-based rules that break when the address keeps changing. Beyond that, the MAC address mostly matters when you are administering your own network: identifying devices in the router's client list, pinning IPs for port forwarding, and spotting unknown hardware on your Wi-Fi. What it never does is follow you onto the internet - Websites see only your public IP, and tracking there is a different battle fought with different tools.
Frequently Asked Questions
Can I change my MAC address?
Yes - Operating systems can override the burned-in address with a locally administered one. Phones and modern desktops do it automatically per network via randomisation, and Linux, macOS, and Windows allow manual spoofing. The hardware address itself is unchanged; only what the OS announces differs.
Can someone track or hack me using my MAC address?
Only within radio range or on the same network: venues can log Wi-Fi MACs to recognise returning devices, which randomisation defeats. Remotely, a MAC is useless to an attacker - It never crosses the internet, grants no access, and reveals at most the device manufacturer via its OUI prefix.
Is a MAC address unique to my device?
The burned-in address is intended to be globally unique - IEEE assigns each manufacturer OUI blocks, and the vendor numbers each interface. In practice duplicates occasionally exist and spoofing is trivial, so networks treat MACs as identifiers of convenience, not proof of identity.