What Is an OUI? How MAC Vendor Lookup Works

2026-07-03

Every MAC address begins with an OUI (Organizationally Unique Identifier) — a 24-bit prefix that the IEEE Registration Authority assigns to a single manufacturer. This is what makes MAC vendor lookup possible.

Why the OUI matters

When a company builds networking hardware, it registers with the IEEE and receives one or more OUIs. Every device it produces uses one of those prefixes, so the first half of a MAC address reliably points back to the maker — Apple, Cisco, Samsung, Raspberry Pi and thousands more.

How the lookup works

A vendor lookup takes the first 6 hex characters of a MAC (the OUI), then searches the IEEE registry for the organization that owns it. Our database mirrors the official IEEE data and is refreshed regularly, covering more than 30,000 registered vendors.

What you can learn

  • The manufacturer name and registered address
  • The IEEE block type (MA-L, MA-M or MA-S)
  • Whether the address is universally or locally administered

Try it now on the homepage, or browse the full vendor directory.