A MAC address (Media Access Control address) is a unique identifier assigned to every network interface card — the hardware inside your Mac, phone, or any device that connects to a network. Unlike an IP address, a MAC address is tied to the physical hardware and operates at the local network level, not across the internet.
Anatomy of a MAC Address
Every MAC address is 48 bits long, written as six pairs of hexadecimal digits separated by colons. Hover over the segments below to see what each part means.
MAC Address vs. IP Address
People often confuse MAC addresses with IP addresses. Here's the key difference:
| Feature | MAC Address | IP Address |
|---|---|---|
| Layer | Layer 2 (Data Link) | Layer 3 (Network) |
| Scope | Local network only | Global (internet) |
| Assigned by | Hardware manufacturer | Your router or ISP |
| Format | 6 hex pairs (48 bits) | 4 decimal octets (IPv4) or 8 hex groups (IPv6) |
| Changes? | Stable (can be spoofed) | Changes per network / session |
| Visible to websites? | No — only your router sees it | Yes — visible to all remote servers |
How Networks Use Your MAC Address
When you connect to a Wi-Fi network, your device broadcasts its MAC address as part of the ARP (Address Resolution Protocol) process. The router uses this to:
- Assign an IP address — DHCP servers often map MAC → IP for consistent internal addressing.
- Identify your device — Routers, network logs, and captive portals can track which physical device is which.
- Apply MAC filtering — Some networks only allow specific MAC addresses to connect.
- Track session time — Hotel, airport, and in-flight Wi-Fi portals use your MAC address to remember how long you've been connected and enforce time limits.
What Is MAC Spoofing?
MAC spoofing is the process of overriding your hardware MAC address with a different one in software. Every modern OS supports this. The change is temporary — your original hardware address comes back when you reboot.
Common legitimate reasons to spoof your MAC address include:
- Resetting a captive portal session (e.g. airplane Wi-Fi time limits)
- Getting unblocked from a network that has blocked your device
- Preventing tracking across public Wi-Fi hotspots
- Network testing and development
- Privacy — stopping retailers from tracking your device as you move through stores
Is It Legal to Change Your MAC Address?
Yes — in almost all jurisdictions, spoofing your own device's MAC address is completely legal. It is a built-in, documented capability of macOS, Linux, and Windows. Apple itself uses MAC address randomisation in iOS and macOS for Wi-Fi scanning to protect user privacy.
The only cases where it becomes legally murky are when you use MAC spoofing to impersonate another specific device, gain unauthorised access to a network, or circumvent security controls on a network you don't own.
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Frequently Asked Questions
Can websites see my MAC address?
No. Websites only see your IP address, not your MAC address. The MAC address is stripped at your router and never leaves the local network. Only devices on the same network segment — like your router, other devices, or a captive portal server — can see it.
Does every device have a unique MAC address?
Globally unique hardware MAC addresses are guaranteed by the IEEE assignment process — manufacturers buy blocks of OUI prefixes and must assign unique device IDs within their block. However, with ~281 trillion possible addresses and spoofing, collisions on a local network are possible but extremely rare.
Why does Apple randomise MAC addresses?
Starting with iOS 14 and macOS Big Sur, Apple randomises the MAC address used for Wi-Fi scanning (probe requests) to prevent retailers and tracking networks from building a movement profile of your device before you connect. This is different from the connected MAC address, which MacSpoof lets you change.
How long is a MAC address?
A MAC address is 48 bits long — 6 bytes — written as 6 pairs of hexadecimal digits. Some newer protocols (EUI-64) use 64-bit extensions, but standard Ethernet MAC addresses are always 48 bits.