MAC Vendor Lookup

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MAC address vendor lookup

MAC Address: How to Identify the Manufacturer From Its 48 Bits

Every MAC address embeds the manufacturer identity in its first bits, a leftover from when every network card shipped from the factory with a fixed, unique number. That still holds for wired hardware today, but a good share of the Wi-Fi around you no longer follows that rule, on purpose.

The 48 bits, the OUI, and the bit that turns the rule off

A MAC address has 48 bits, written as 6 hex pairs. The first 24 bits (the first 3 octets) form the OUI, an identifier IEEE assigns exclusively to a single manufacturer in the MA-L registry, with the smaller MA-M and MA-S registries reserved for organizations that need fewer addresses. The prefix 3C:5A:B4, for instance, belongs to Google, Inc. in the current registry, which holds more than 52 thousand organizations sourced directly from the CSV files IEEE itself publishes.
The second-least-significant bit of the first octet, the U/L bit, states whether the address is universally administered by the manufacturer (bit at 0) or locally (bit at 1). A MAC starting with 02 in hex, which is 00000010 in binary, has that second bit at 1: by definition, any address like this is local, with no relation to the manufacturer that made the physical card.
The real trap: modern phones and laptops (iOS, Android, and Windows network privacy feature) generate a new, locally-administered MAC for every different Wi-Fi network they join, instead of broadcasting the real factory OUI. A lookup on that randomized address correctly returns "no matching vendor", which is the privacy feature working as designed, not a gap in the OUI database.

Three addresses, three different origins

Real factory prefix

Input: 3C:5A:B4:11:22:33
Expected output: OUI 3C5AB4, registro MA-L, fabricante Google, Inc.

U/L bit at 0 (universal), so the address was burned in directly by the manufacturer that registered this OUI with IEEE.

Randomized privacy MAC

Input: 02:1A:2B:3C:4D:5E
Expected output: bit U/L = 1 (local), sem fabricante correspondente na base

Typical pattern for per-network MAC randomization: no real vendor generates addresses like this, so the missing result is expected, not a lookup error.

Reserved broadcast address

Input: FF:FF:FF:FF:FF:FF
Expected output: endereço reservado de broadcast, entregue a todo dispositivo do segmento

All 48 bits set to 1 is the single value reserved for Ethernet broadcast; it never belongs to a manufacturer, so looking up a vendor for it makes no sense.

Full tool FAQ

Does the tool identify a vendor from the MAC prefix?

Yes. It uses the registered prefix to indicate which organization received that block, when that interpretation is meaningful for the address type provided.

What is an OUI in a MAC address?

Does a MAC always reveal the real device vendor?

What is the difference between a universal and a local MAC?

Why can phones and laptops use randomized MAC addresses?

Do broadcast and multicast addresses have a vendor?

Can a MAC address prove device identity?

When is MAC vendor lookup most useful?

How does a MAC become an IPv6 link-local address?

How do you generate a valid locally administered MAC?

Frequently asked questions

Why does my MAC change every time I join a different Wi-Fi?

Because the operating system generates a new locally-administered address per network, a privacy feature meant to stop the same device from being tracked across different networks using just the factory MAC.

What are the first 24 bits of a MAC?

They are the OUI, a block IEEE assigns exclusively to a manufacturer. That part alone is what a vendor lookup uses to identify who made the network card.

Are MA-L, MA-M and MA-S the same thing?

No. They are three block sizes IEEE sells to manufacturers: MA-L covers a 24-bit prefix, and the smaller MA-M and MA-S options exist for organizations that need fewer addresses than a full MA-L block provides.

Can two devices share the same MAC address?

In theory, no, for factory addresses: each OUI belongs to one manufacturer, which in turn does not repeat the final 24 bits. But locally-generated addresses, like Wi-Fi randomization or virtual machine MACs, do not come from the IEEE registry and can collide.

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MAC address vendor lookup

MAC Address: How to Identify the Manufacturer From Its 48 Bits

The 48 bits, the OUI, and the bit that turns the rule off

A MAC address has 48 bits, written as 6 hex pairs. The first 24 bits (the first 3 octets) form the OUI, an identifier IEEE assigns exclusively to a single manufacturer in the MA-L registry, with the smaller MA-M and MA-S registries reserved for organizations that need fewer addresses. The prefix 3C:5A:B4, for instance, belongs to Google, Inc. in the current registry, which holds more than 52 thousand organizations sourced directly from the CSV files IEEE itself publishes.

The second-least-significant bit of the first octet, the U/L bit, states whether the address is universally administered by the manufacturer (bit at 0) or locally (bit at 1). A MAC starting with 02 in hex, which is 00000010 in binary, has that second bit at 1: by definition, any address like this is local, with no relation to the manufacturer that made the physical card.

The real trap: modern phones and laptops (iOS, Android, and Windows network privacy feature) generate a new, locally-administered MAC for every different Wi-Fi network they join, instead of broadcasting the real factory OUI. A lookup on that randomized address correctly returns "no matching vendor", which is the privacy feature working as designed, not a gap in the OUI database.

Three addresses, three different origins

Real factory prefix

Input: 3C:5A:B4:11:22:33
Expected output: OUI 3C5AB4, registro MA-L, fabricante Google, Inc.

U/L bit at 0 (universal), so the address was burned in directly by the manufacturer that registered this OUI with IEEE.

Randomized privacy MAC

Input: 02:1A:2B:3C:4D:5E
Expected output: bit U/L = 1 (local), sem fabricante correspondente na base

Typical pattern for per-network MAC randomization: no real vendor generates addresses like this, so the missing result is expected, not a lookup error.

Reserved broadcast address

Input: FF:FF:FF:FF:FF:FF
Expected output: endereço reservado de broadcast, entregue a todo dispositivo do segmento

All 48 bits set to 1 is the single value reserved for Ethernet broadcast; it never belongs to a manufacturer, so looking up a vendor for it makes no sense.

Full tool FAQ

Does the tool identify a vendor from the MAC prefix?

Yes. It uses the registered prefix to indicate which organization received that block, when that interpretation is meaningful for the address type provided.

What is an OUI in a MAC address?

Does a MAC always reveal the real device vendor?

What is the difference between a universal and a local MAC?

Why can phones and laptops use randomized MAC addresses?

Do broadcast and multicast addresses have a vendor?

Can a MAC address prove device identity?

When is MAC vendor lookup most useful?

How does a MAC become an IPv6 link-local address?

How do you generate a valid locally administered MAC?

Frequently asked questions

Why does my MAC change every time I join a different Wi-Fi?

What are the first 24 bits of a MAC?

They are the OUI, a block IEEE assigns exclusively to a manufacturer. That part alone is what a vendor lookup uses to identify who made the network card.