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MAC Address (OUI) Decoder

Resolve a MAC address to its vendor and inspect the meaning of its bits.

Network, System & PacketsFree
INPUT
OUTPUT

The result appears here as you type.

Decoding runs in your browser. What you paste is not sent to a server.

A MAC address decoder splits a 48-bit hardware address into its Organizationally Unique Identifier (the first three bytes, which identify the manufacturer) and the device-specific remainder, and reads the flag bits that mark local and multicast addresses.

Example

Input
F0:9F:C2:AB:CD:EF
Output
OUI (vendor prefix): F09FC2
Device ID: ABCDEF
Cast: Unicast
Administration: Globally unique

What is the MAC Address (OUI) Decoder?

A MAC address is six bytes, conventionally written as hex pairs separated by colons or hyphens. The first three bytes are the OUI, assigned by the IEEE to a manufacturer; the last three are assigned by that manufacturer to individual interfaces. Looking up the OUI tells you who made the network interface — often enough to identify a device on a network you don't fully control.

Two bits in the first byte carry meaning. The least significant bit marks a multicast address (01:00:5E prefixes are IPv4 multicast, 33:33 is IPv6). The next bit up is the locally administered flag: when set, the address was assigned by software rather than burned in by the manufacturer, and OUI lookup is meaningless.

That second bit is now everywhere. iOS, Android, Windows and macOS all randomise MAC addresses when scanning for and joining Wi-Fi networks, precisely to defeat the location tracking that stable MACs enabled. A randomised address always has the locally administered bit set.

How to use the MAC Address (OUI) Decoder

  1. Paste the MAC address in any format: colons, hyphens, dots or bare hex.
  2. Read the vendor resolved from the OUI, if the address is globally assigned.
  3. Check the local bit — if it is set, the address is randomised and has no real vendor.

When to use it

  • Identifying an unknown device on a network from its hardware vendor.
  • Explaining why a device shows a different MAC on each connection.
  • Confirming whether a captured address is multicast or unicast.

MAC Address (OUI) Decoder at a glance

Length48 bits — 6 bytes, 12 hex digits
OUIFirst 3 bytes, IEEE-assigned to a vendor
Multicast bitLeast significant bit of the first byte
Local bitSecond-least bit — set means randomised/software-assigned

Frequently asked questions

Why does my phone's MAC address keep changing?

Modern mobile operating systems randomise the MAC per network to prevent passive location tracking. Randomised addresses always have the locally administered bit set, so OUI lookup returns nothing.

Can a MAC address be spoofed?

Trivially — it is a software-settable field on essentially every operating system. MAC-based access control is a convenience, never a security boundary.

What does an OUI actually tell me?

The company that registered the address block, which is the maker of the network chipset or the device — not necessarily the brand on the case, since many vendors use third-party radios.

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