MAC Lookup

MAC Lookup online: find a manufacturer by MAC address

Every network adapter — Wi-Fi, Ethernet, Bluetooth — has a unique 48-bit (6-byte) MAC address (Media Access Control). The first three bytes are the OUI (Organizationally Unique Identifier), a block IEEE assigns to a specific hardware manufacturer. The OUI prefix reveals who made a network card, router, IoT device, or smartphone, without needing access to its settings.

MAC address structure

• First 3 bytes (OUI) — the manufacturer identifier registered with IEEE
• Last 3 bytes — a unique serial number the manufacturer assigns within its own OUI
• I/G bit (lowest bit of the first byte) — 0 means unicast (a regular device), 1 means multicast/broadcast
• U/L bit (second bit of the first byte) — 0 means a factory-assigned universal address with a real OUI, 1 means locally administered, i.e. assigned in software rather than by the manufacturer

Why modern phones show an "unknown" vendor

Since iOS 14 and Android 10, devices use a randomized MAC address by default when connecting to new Wi-Fi networks — a privacy feature that prevents access-point owners from tracking a device by a persistent MAC across different networks. Such addresses always have the U/L bit set (locally administered) and intentionally don't carry the device's real OUI.

Frequently asked questions

• What is an OUI?

  The first 3 bytes of a MAC address — a manufacturer identifier assigned by IEEE. The remaining 3 bytes are a serial number the manufacturer assigns.

• Why wasn't the vendor found?

  Either the OUI isn't in the database (a curated subset, not the full IEEE registry), or the address is locally administered — randomly generated rather than manufacturer-issued.

• What is a locally administered address?

  Second bit of the first byte = 1 means a software-assigned address (OS, hypervisor, Wi-Fi privacy MAC), not a factory OUI.

See also

• IP ↔ Binary/Hex — IP address conversion
• WebRTC Leak Test — check for real IP leaks
• User-Agent — browser and device info