MAC Address vs IP Address: What's the Difference

Your device has both a MAC address and an IP address. They serve different purposes at different layers of the network model. Understanding the distinction clarifies why you can't track someone across the internet using their MAC address — and why MAC addresses matter more than you'd think for local network tracking.

What a MAC Address Is

A MAC (Media Access Control) address is a hardware identifier burned into your network interface card during manufacture. It's 6 bytes — 48 bits — expressed as six pairs of hexadecimal digits, like 00:1A:2B:3C:4D:5E. The first three bytes identify the manufacturer (the OUI — Organisationally Unique Identifier). The last three are a unique identifier assigned by the manufacturer.

MAC addresses operate at Layer 2 of the network model — the data link layer. They're used for communication within a local network segment. Your device's MAC address is how your router knows which physical device to send packets to on your LAN.

The Key Difference in Scope

IP addresses are routable across the internet. MAC addresses are not. When a packet leaves your router for the internet, your device's MAC address goes with it only as far as the first router hop — at that point, the router strips the original MAC addressing and substitutes its own. MAC addresses don't propagate through routers.

This is why websites can't see your MAC address. The MAC address never leaves your local network. What websites see is your public IP — assigned by your ISP, shared across your household, and managed by your router.

MAC Address Privacy

Within your local network, though, MAC addresses are fully exposed. Wi-Fi access points can log the MAC addresses of every device that connects. Public Wi-Fi hotspots have historically used MAC addresses to track returning visitors, enforce time limits, and build profiles of repeat customers.

Modern mobile operating systems (iOS since iOS 14, Android since Android 10) use MAC address randomisation for Wi-Fi — each network connection uses a randomly generated MAC instead of the hardware MAC. This prevents tracking across networks. Windows also added MAC randomisation, but it's not always enabled by default depending on the version.

MAC Spoofing: Changing What the Network Sees

MAC addresses can be changed in software on most operating systems — this is called MAC spoofing. On Linux, 'ip link set dev eth0 address XX:XX:XX:XX:XX:XX'. On Windows, some network adapter drivers allow it through the Device Manager advanced settings. On macOS, the ifconfig command can do it temporarily. The change is reversible — rebooting usually restores the original hardware MAC.

MAC spoofing is used legitimately to bypass MAC-based network access controls — corporate environments that whitelist specific MAC addresses, or ISPs that tie their service to a specific modem's MAC. It's also used by penetration testers to impersonate authorised devices on a network. Modern operating systems' automatic MAC randomisation does the same job automatically for privacy, without requiring manual commands — which is why understanding that iOS 14 randomises MACs by default is relevant if you're managing a network that uses MAC-based authentication.