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IT Tool

MAC Address Vendor Lookup - OUI and Address Decoder

Look up the manufacturer behind a MAC address or OUI, and decode the address locally: unicast vs multicast, and universally vs locally administered, so randomized addresses are named as such instead of shown as an error.

Instant AI-Assisted No Login
PROCESSINGSERVER / AI
LIMITNONE
PRIVACYSEE NOTES

MAC address or OUI

What a MAC address is, and what it can honestly tell you

A MAC address is the hardware identifier a network interface uses to talk to other devices on the same local network segment, the Ethernet or Wi-Fi link right in front of it. It is 48 bits long, written as six pairs of hexadecimal digits like 00:1A:2B:3C:4D:5E. Unlike an IP address, which can change as a device moves between networks, the MAC address is meant to stay with the interface, and it is used for delivery within a single segment rather than for routing across the internet.

The address splits cleanly in half. The first 24 bits are the Organizationally Unique Identifier, the OUI, which the IEEE assigns to a company. The last 24 bits are that company’s to allocate, one per interface, so the whole address is unique. Because the maker lives entirely in the first half, a vendor lookup only ever needs those first six hex characters, which is why this tool accepts a bare OUI prefix as readily as a full address.

It is worth being clear about the limits up front. A successful lookup tells you which company registered the block, and it can show that company’s registered mailing address, which is a corporate office, not the device. It does not reveal where the device is, what its IP address is, or who owns it. A MAC address is a manufacturing label, not a locator.

Two bits you can read without any lookup

The very first octet carries two flags in its two lowest bits. The least-significant bit is the cast bit: 0 is a unicast address bound to one interface, 1 is a multicast group address. The next bit up is the universal/local bit: 0 means the address was universally administered and handed out by the IEEE, 1 means it was locally administered, set by software. This tool decodes both straight from the digits you type, which is why the “read from the address itself” panel appears before any network result.

Why randomized addresses are not a lookup failure

Modern phones and laptops rotate a randomized MAC on Wi-Fi to stop venues tracking them across visits. Those addresses are generated with the locally-administered bit set, and by definition a locally administered address has no manufacturer registration. So an empty vendor result there is the correct answer, not a gap in the database. Reading the bit lets the tool label the address as locally administered instead of showing a misleading “unknown vendor”, which is the single most common source of confusion with these tools.

The three outcomes, and why they are different

A lot of lookup tools flatten everything into “found” or “unknown”, which hides the most useful information. There are really three distinct answers, and this tool keeps them apart. The first is a registered vendor: the OUI maps to a company in the IEEE registry, and you get its name, its registered address, the block type, and when the registry entry was last updated. That is the clean hit.

The second is a locally administered address. Its universal/local bit is set, so it was never meant to carry a vendor at all. This is what randomization produces, and it is a definite answer rather than a maybe: there is no manufacturer to find because the address was minted by software. Treating this as the same as a missing record would throw away the one thing the address is actually telling you.

The third is an unregistered prefix: the address looks universally administered, so it should have a vendor, but no assigned block matches it. That points to a typo, a brand-new assignment the registry copy has not caught up with, or a genuinely unallocated range. Because the cause is different from a randomized address, the fix is different too, usually just re-checking the digits you entered.

Registration block sizes

When a vendor is found, the block type says how big a slice of address space the company bought:

  • MA-L (large): a full 24-bit OUI, roughly sixteen million addresses. The classic assignment for high-volume manufacturers.
  • MA-M (medium): one OUI split across several companies using a few more bits, for makers who do not need a whole block.
  • MA-S (small): a 36-bit assignment, about a million addresses, aimed at lower-volume producers.

For MA-M and MA-S, the same leading OUI can belong to different companies, which is why a precise lookup uses more than the first six digits and why the registry, not the prefix alone, has the final say on the vendor.

Where this fits in a network workflow

The everyday use is putting a name to a device you see on your own network. A router’s client list or an ARP table shows MAC addresses, and resolving the OUIs turns a wall of hex into “that’s the printer, that’s a laptop, that’s a smart plug”. Where you instead see a cluster of locally administered addresses, that is usually phones cycling randomized MACs rather than unknown intruders, and the local decode makes that obvious without a lookup.

Keep the boundary in mind: a MAC address normally stays on the local segment and does not travel across the internet, so you can only look up addresses you can already see on your own network. To investigate what a connection exposes beyond the local link, the What Is My IP tool shows the public address the wider internet sees, and the DNS Lookup tool resolves the records behind a domain name.

How to Use

1

Enter a full MAC address or just the 6-character OUI prefix, in any common format (00:1A:2B:3C:4D:5E, 00-1A-2B, or 001A2B).

2

Press Look up or hit Enter.

3

Read the local decode first: it tells you unicast vs multicast and universal vs locally administered from the address alone.

4

Then read the registry outcome: a registered vendor with its block details, a locally administered address with no vendor by design, or an unregistered prefix.

Features

Decodes the cast bit and the universal/local bit from the first octet with no network call
Names a randomized or software-set address as locally administered instead of a false "unknown vendor"
Separates three real outcomes: registered vendor, locally administered, and unregistered prefix
Shows the IEEE block type (MA-L, MA-M, MA-S) and last registry update when a vendor is found
Accepts full addresses or bare OUI prefixes in colon, hyphen, dot, or plain-hex form
Rate-limited server lookup against the IEEE registry; no query history is stored

Common Questions

Use this MAC address vendor lookup to identify the manufacturer behind an OUI and to decode the address itself: whether it is unicast or multicast, and whether it is a universally administered hardware address or a locally administered one set by software. That distinction is what tells you a randomized phone or laptop address apart from a genuine vendor miss, so the result is a diagnosis rather than a bare unknown. Enter a full MAC address or just the six-character OUI prefix.

About MAC Address Lookup

Identify the hardware manufacturer behind a MAC address or OUI, and decode the address itself before any lookup: the cast bit (unicast vs multicast) and the universal/local bit (IEEE-assigned vs software-set) are read straight from the first octet. That distinction separates three real outcomes instead of a bare found-or-unknown: a registered vendor with its IEEE block type and last update, a locally administered address that has no vendor by design (what phone and laptop MAC randomization produces), and a universally administered prefix that simply is not in the registry. Accepts full addresses or bare OUI prefixes in colon, hyphen, dot, or plain-hex form.

Also known as: mac address vendor, mac vendor lookup, find device manufacturer, oui lookup, oui vendor, mac address manufacturer, identify device by mac, mac randomization check, locally administered address, mac prefix lookup, ieee oui, network card vendor.

Processing Note

MAC Address Lookup may rely on server-side, model-based, or external processing for part of its workflow, so avoid entering secrets, credentials, or private personal data.

Tool Limits

IT tools provide quick diagnostics and transformations. They cannot see every private network, deployment setting, proxy, firewall, or production edge case.

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