The first three bytes, assigned to a manufacturer by the IEEE. It identifies who made the network interface, not the device model.

Why does my phone MAC change?

Privacy randomisation. The phone generates a locally administered address per network, which is marked by a bit in the first byte, so it cannot be tracked across networks.

Technologynetworking

MAC Address Formatter

MAC address reformatting between the four common notations. The first three bytes are the manufacturer identifier, and the second-least-significant bit of the first byte says whether the address is globally unique or locally assigned.

Also called: mac address converter, format mac address.

Formatted

00:1A:2B:3C:4D:5E

00:1A:2B:3C:4D:5E. The OUI is 00:1A:2B, identifying the manufacturer, and the device portion is 3C:4D:5E. This is a globally unique address assigned by the manufacturer.

Organisationally unique identifier

00:1A:2B

Device identifier

3C:4D:5E

In every format

00:1A:2B:3C:4D:5E | 00-1A-2B-3C-4D-5E | 001A.2B3C.4D5E | 001A2B3C4D5E

On the address type

This is a globally unique address assigned by the manufacturer.

On privacy

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How this is calculated

Method and background

How this is calculated

A MAC address is six bytes written four different ways depending on the vendor tooling. The first three bytes are the organisationally unique identifier assigned to a manufacturer, and the last three identify the device. Two bits in the first byte carry meaning: the least significant marks a multicast address, and the next one marks a locally administered address, which is what randomised privacy MACs on phones set.

the first three bytes identify the manufacturer and the last three the device

OUI: Organisationally unique identifier

Worked examples

Each of these is asserted on every build. If a change to the engine ever moved one of these answers, the build would fail before the page could print it.

reformatting to Cisco notation

MAC address: 00:1A:2B:3C:4D:5E
Output format: Cisco dotted
Uppercase: Yes

Formatted001A.2B3C.4D5E

Four hex digits per group, three groups

Open this example

a locally administered address is detected

MAC address: 02:1A:2B:3C:4D:5E
Output format: Colon separated
Uppercase: Yes

Formatted02:1A:2B:3C:4D:5E

boundary: bit 1 of the first byte is set

Open this example

Method and limits

What it assumes

A 48-bit MAC address. EUI-64 addresses are eight bytes and not handled.

What it deliberately does not model

OUI lookup requires the IEEE registry, which this does not include.

Formula version 1.0.0 · definition 1.0.0 · India · Report a problem with this calculator

Frequently asked questions

What is the OUI?: The first three bytes, assigned to a manufacturer by the IEEE. It identifies who made the network interface, not the device model.
Why does my phone MAC change?: Privacy randomisation. The phone generates a locally administered address per network, which is marked by a bit in the first byte, so it cannot be tracked across networks.