MAC Addresses - Your Device's Hardware Fingerprint
The permanent ID burned into every network device
What Is a MAC Address?
A MAC address (Media Access Control address) is a unique identifier assigned to the network hardware in your device. Every WiFi chip, Ethernet port, and Bluetooth adapter has its own MAC address.
It looks like this: A4:83:E7:2B:9F:01 - six pairs of letters and numbers separated by colons.
Think of it as a serial number for your device's network card. While your IP addressThe address assigned by DHCP that can change each time you connect. More Info… can change every time you connect, your MAC address stays the same.
Who Decides the MAC Address?
The manufacturer of your network hardware assigns the MAC address at the factory. It's written into the chip during production.
The first three pairs (e.g., A4:83:E7) identify the manufacturer. This is called the OUI (Organizationally Unique Identifier). For example:
- Apple devices might start with A4:83:E7
- Intel network cards might start with 00:1B:21
- Samsung devices might start with 8C:F5:A3
The last three pairs are a unique serial number assigned by that manufacturer.
Where Is It Physically Stored?
The MAC address is burned into the firmware of the network chip itself during manufacturing. It's stored in a small read-only memory on the network card. You can't see it physically printed on most devices, but your operating system can read it from the chip.
Why Do We Need MAC Addresses When We Have IP?
Great question. Here's the key difference:
- IP addresses can change - Every time you connect to a network, DHCPThe service that automatically assigns IP addresses. More Info… might give you a different IP
- MAC addresses are permanent - They identify the physical hardware itself
On your local network, devices actually use MAC addresses to send data to each other at the lowest level. When your laptop wants to send data to your printer on the same network, it uses the printer's MAC address to deliver the data directly.
IP addresses are like a name you go by (can change), MAC addresses are like your fingerprint (always the same).
Does MAC Work on the Internet?
No. MAC addresses only work on your local network (LAN)The network inside your home - devices connected to your router. More Info…. When your data leaves your home router and goes out to the internet, your router strips your device's MAC address and replaces it with its own.
Each hop on the internet only sees the MAC address of the device immediately before it. So a website like Google has no way to see your laptop's MAC address - only your ISP's equipment's MAC address.
Can Two Devices Have the Same MAC Address?
In theory, no. Every manufacturer is supposed to assign unique MAC addresses. With 281 trillion possible combinations, there's plenty of room.
In practice, duplicates are extremely rare but can happen due to:
- Manufacturing errors - Very rare, but documented cases exist
- MAC spoofing - Software can override the hardware MAC with a custom one (used for privacy or testing)
- Virtual machines - Software-created computers that generate their own MAC addresses
If two devices with the same MAC address end up on the same local network, both will have connectivity problems. But since MAC addresses don't travel past your router, duplicates on different networks cause no issues.