MAC Address Analyzer

Learn about MAC addresses

What this is actually decoding

A MAC address is 48 bits, six bytes, usually written as pairs of hex digits. The first three bytes are the OUI (Organizationally Unique Identifier), a block assigned by the IEEE to a specific manufacturer, which is why looking one up can often reveal the vendor of the device it came from.

The two bits that change everything

The first byte carries two special bits. The least significant bit is the I/G bit: 0 means the address belongs to one specific device (unicast), and 1 means it's a group address (multicast or broadcast). The next bit is the U/L bit: 0 means it's a globally unique address assigned by the manufacturer, and 1 means it's locally administered, meaning software set it rather than the factory burning it in.

Common questions

Why does my device show a different MAC address every time I check it? Most modern phones and laptops use MAC address randomization for Wi-Fi scanning and new network connections, specifically to prevent tracking. A locally administered address (the U/L bit set to 1) is usually the sign this is happening.

Can two devices ever share the same MAC address? They shouldn't, by design, since factory-assigned addresses are meant to be globally unique. It does happen occasionally through manufacturing errors or intentional cloning, and it causes real network conflicts when it does.

Is the vendor lookup always accurate? Only as accurate as the IEEE's public OUI registry and how current it is, and it won't identify anything for a locally administered, randomized address, since those aren't tied to any manufacturer block at all.