MAC address lookup

Every network interface has a MAC address, and its first 24 bits, the Organizationally Unique Identifier (OUI), are assigned by the IEEE to the manufacturer. Looking up the OUI tells you who made a device, which is very useful when you find an unknown entry in your router's client list, a switch's MAC table or a DHCP log.

How to use it

1. Paste a MAC address in any common format.
2. Read the vendor name associated with its OUI.

How the lookup works

The tool takes the first three bytes of the address, for example B8:27:EB from B8:27:EB:12:34:56, and searches the IEEE registry. B8:27:EB is registered to the Raspberry Pi Foundation, so the device is very likely a Raspberry Pi. The remaining three bytes are a serial number chosen by the manufacturer.

Why a lookup can return nothing or the wrong answer

• Randomised addresses: phones, tablets and laptops use private, random MAC addresses on Wi-Fi. If the second hex digit is 2, 6, A or E, the address is locally administered and has no vendor.
• Chip vendor, not brand: the OUI often belongs to the maker of the network chip, such as Espressif, Realtek or Intel, not the brand on the box. Many smart plugs and bulbs show up as Espressif devices.
• Virtual machines show the hypervisor vendor, such as VMware or QEMU.
• Larger blocks: some vendors have MA-M or MA-S assignments that use 28 or 36 bits.

Security tip

An unknown device on your network is not necessarily an intruder; it is often a smart TV or IoT gadget. Match it with its IP address and hostname, then check your devices one by one. MAC addresses can be spoofed, so a vendor match is a hint, not proof.