MAC Address OUI Lookup
Identify the manufacturer of any network device from its MAC address using the IEEE OUI registry — instant, offline, no API required.
What is a MAC address?
A MAC (Media Access Control) address is a unique hardware identifier permanently assigned to a network interface controller (NIC). Every Ethernet card, Wi-Fi adapter, and Bluetooth radio ships from the factory with a MAC address baked into its firmware.
MAC addresses are 48-bit numbers written as six pairs of hexadecimal digits. The most common formats you will encounter are:
- Colon-separated:
00:1B:63:84:45:E6 - Hyphen-separated:
00-1B-63-84-45-E6 - Plain hex:
001B638445E6
While IP addresses are assigned dynamically and route traffic across the internet, MAC addresses identify devices on a single network segment (a LAN, a VLAN, or a Wi-Fi access point). Switches use MAC addresses to direct frames to the correct physical port. Routers use IP addresses to move packets between networks.
What is an OUI and how does IEEE manage it?
An OUI (Organizationally Unique Identifier) is the first 24 bits — the first three octets — of a MAC address. The IEEE Registration Authority assigns OUI blocks to hardware manufacturers for a one-time fee. Once assigned, all MAC addresses starting with that prefix officially belong to that organisation.
The IEEE MA-L (MAC Address Large) block contains the standard 24-bit OUI assignments. There are also MA-M (28-bit) and MA-S (36-bit) blocks for organisations that need fewer addresses. This tool uses the MA-L registry, which covers the vast majority of consumer and enterprise hardware.
Example OUI breakdown
For B8:27:EB:12:34:56:
B8:27:EB— OUI prefix, assigned to Raspberry Pi Foundation12:34:56— Device-specific suffix, assigned by the manufacturer
This tells you the device is a Raspberry Pi board, even if you know nothing else about it. This is invaluable when identifying unknown devices on a network scan.
IEEE updates the registry several times per week as manufacturers purchase
new blocks. Run node scripts/update-oui.js
to refresh the local database.
Common use cases for MAC vendor lookup
Network discovery and inventory
- Identify unknown devices discovered by a network scanner (Nmap, Angry IP Scanner)
- Match a MAC address from DHCP logs to a manufacturer for device classification
- Verify that a new device on the network belongs to an expected vendor
- Build or validate a hardware inventory spreadsheet
Security and incident response
- Identify rogue or unauthorised devices on a corporate network
- Determine whether an unknown MAC belongs to legitimate hardware
- Flag locally administered MACs that may indicate MAC spoofing
- Correlate MAC addresses in firewall and switch logs with vendors
Troubleshooting and support
- Confirm the NIC vendor when troubleshooting driver or compatibility issues
- Identify Wi-Fi chipset vendor when diagnosing wireless performance problems
- Match a client MAC from an access point log to a device type
- Verify that a virtual machine is using a VMware or VirtualBox OUI prefix
Development and IoT
- Verify the OUI assigned to custom hardware before mass production
- Identify ESP32/ESP8266 modules on a development network
- Check whether a MAC randomisation policy is working as expected
- Cross-reference embedded device MAC addresses in firmware analysis
Frequently asked questions
What is a MAC address?
A MAC (Media Access Control) address is a unique hardware identifier assigned to
a network interface. It is a 48-bit number written as six pairs of hexadecimal
digits — for example, 00:1B:63:84:45:E6.
Every network adapter ships from the factory with a globally unique MAC address
encoded in its firmware or hardware.
MAC addresses operate at Layer 2 (the data link layer) of the OSI model and are used to identify devices on a local network segment. Unlike IP addresses, they do not cross router boundaries.
What is an OUI?
An OUI (Organizationally Unique Identifier) is the first three octets (24 bits) of a MAC address. The IEEE Registration Authority sells 24-bit OUI blocks to manufacturers, who then use them as a prefix for all MAC addresses assigned to their hardware.
The remaining three octets are assigned by the manufacturer, giving each OUI block 16.7 million unique addresses. Large manufacturers like Cisco or Apple hold hundreds of OUI blocks.
What MAC address formats does this tool accept?
The tool accepts all common MAC address formats:
- Colon-separated:
00:1B:63:84:45:E6 - Hyphen-separated:
00-1B-63-84-45-E6 - Plain hex (no separator):
001B638445E6
Input is case-insensitive and separators are stripped automatically before the lookup. The result always displays the normalised colon-separated format.
Why does the tool show "locally administered address"?
If the second-least-significant bit of the first octet is set (bit 1), the MAC is locally administered — it was assigned by software, not by the hardware manufacturer. Locally administered MACs do not have IEEE OUI registrations.
Common sources of locally administered MACs:
- Virtual machines (VMware static MACs starting with
02:) - Docker and Linux bridge interfaces
- Wi-Fi privacy/randomisation (iOS, Android, Windows 10/11, macOS)
- Manually configured MAC addresses
What is a multicast MAC address?
A multicast MAC address has the least-significant bit of the first octet set to 1. Multicast frames are delivered to a group of devices on the same network segment rather than to a single destination.
Common multicast prefixes:
01:00:5E:xx:xx:xx— IPv4 multicast33:33:xx:xx:xx:xx— IPv6 multicast01:80:C2:00:00:0x— Spanning Tree Protocol00:00:5E:00:01:xx— VRRP virtual router MAC
Why might the vendor not appear in the results?
The bundled seed database covers common vendors but is not exhaustive. If a vendor is not found, the most likely reasons are:
- The OUI belongs to a smaller or regional manufacturer not in the seed
- The OUI was recently assigned and the database has not been updated
- The MAC is locally administered (no IEEE registration exists)
- The device uses MAC address randomisation
Running node scripts/update-oui.js
downloads the complete IEEE MA-L registry with 30,000+ entries, which covers
virtually all globally unique MAC addresses.
Does MAC address randomisation affect this tool?
Yes. Modern operating systems including iOS, Android, Windows 10/11, and macOS use randomised MAC addresses when connecting to Wi-Fi networks to prevent tracking across different networks and access points.
A randomised MAC has the locally administered bit set and will appear as "Locally Administered" in this tool — it will not match any IEEE OUI. The device's actual hardware manufacturer cannot be determined from a privacy MAC address.
How do I find the MAC address of my device?
Common methods to find your device's MAC address:
- Windows: Open Command Prompt and run
ipconfig /all— look for "Physical Address" - macOS: System Settings → Network → select interface → Details → Hardware
- Linux: Run
ip link showorifconfig - iOS: Settings → General → About → Wi-Fi Address
- Android: Settings → About Phone → Status → Wi-Fi MAC Address