Find the vendor name of a device by entering an OUI or a MAC address
What is the difference between an OUI and a MAC address?
An OUI is a 24-bit number the IEEE assigns to one organization. It is not an address and identifies nothing on a network by itself. A MAC address is a 48-bit identifier of a network interface, and its first 24 bits usually carry the OUI of the organization that registered the block it came from. The OUI is a part of the address, not another name for it.
Two lengths, two jobs
| OUI | 24 bits, three octets | Assigned by the IEEE to an organization |
| MAC address | 48 bits, six octets | Identifies an interface on a local network |
The relationship is positional. In 00:1A:2B:3C:4D:5E the first three octets, 00:1A:2B, are the OUI and the last three are assigned by the organization that holds it. Look that prefix up and it resolves to Ayecom Technology Co., Ltd., the registrant of the 00:1A:2B block. The OUI alone names the organization; the full address names an interface that organization's block covers.
When the first 24 bits are not an OUI
The IEEE issues assignments of other lengths, and a lookup tests each of them rather than assuming three octets. A MA-M block is 28 bits and a MA-S block is 36, so for an address from one of those the registrant is named by the first seven or nine hexadecimal digits instead. 38:B1:4E is such a case: six digits resolve to the IEEE Registration Authority, which holds the parent block, while 38:B1:4E:6 resolves to Universal Robots A/S, the organization the smaller 28-bit block was assigned to. The block sizes covers the three lengths.
A CID is 24 bits like an OUI but is not used the same way: it cannot generate globally unique MAC addresses, because the identifiers derived from it are locally administered. CID and IAB assignments explains why.
They are not interchangeable
Saying "the OUI of this device" is shorthand for the OUI in the address the device presents. The OUI belongs to an organization and outlives any product; the address belongs to an interface and can be replaced, randomized or cloned. An organization may also hold several OUIs at once, so two addresses from the same maker need not share a prefix. What an OUI is covers how one is assigned, and what a MAC address is covers the bits inside it.
Look one up
Enter the first six hexadecimal digits in the MAC address lookup to see the organization they are registered to, or query the prefix through the MACLookup API.
Related questions
Sources and review
Last reviewed: . Technical claims on this page follow the primary sources below; operating-system interfaces change between releases, so check them against your own device version.