Networking Fundamentals
What Is a MAC Address?
Every network adapter has a MAC address — a permanent hardware ID that works alongside, but very differently from, your IP address.
Hardware's permanent name
A MAC address (Media Access Control address) is a unique identifier assigned to a network interface — your Wi-Fi or Ethernet adapter — usually at the factory. It looks like six pairs of hexadecimal digits: 3C:5A:B4:1F:9E:20. The first half identifies the manufacturer; the second half is unique to the device.
MAC vs. IP: two kinds of address
The two work at different layers and serve different purposes:
- A MAC address is tied to the physical hardware and is used for delivery within a single local network.
- An IP address is assigned by the network and is used to route data across networks, all the way to the internet.
An analogy: the IP address is like the mailing address that gets a letter to your building, while the MAC address is like the specific person's name that ensures it reaches the right hands once it arrives locally.
How they work together
When your device sends data to another device on the same local network, it needs that device's MAC address. A protocol called ARP (Address Resolution Protocol) asks, "Who has this IP address?" and the owner replies with its MAC. The data is then framed and delivered locally. Cross the boundary to another network, and routers take over using IP addresses.
Privacy and MAC randomization
Because a MAC address is a stable identifier, it can be used to track a device across Wi-Fi networks. To counter this, modern phones and laptops use MAC randomization, presenting a different, random MAC to each network they join. It is a small but meaningful privacy improvement.
Does a website see my MAC address?
No. MAC addresses do not travel beyond your local network — they are replaced at each hop. A website you visit sees your public IP address, never your MAC. That is a common and reassuring point of confusion to clear up.