iseeu.cc

MAC Address Lookup

Paste one or more MAC addresses to see which organization the IEEE lists for each prefix, the block size, and whether the address is randomized, multicast or broadcast. Matching happens in your browser, and the address itself is never sent anywhere.

Matched in your browser against a bundled copy of the IEEE registry.

What it does

Every Ethernet or Wi-Fi interface carries a 48-bit hardware address, normally written as six pairs of hex digits such as 00:1A:2B:3C:4D:5E. The leading part is a block the IEEE Registration Authority assigned to one organization; the rest is chosen by that organization for each interface it builds. The tool finds the block a prefix falls in and tells you who registered it.

The data is a copy of the IEEE public assignment listings, dated June 2026, covering all three block sizes: MA-L (24-bit prefix, the block long known as an OUI), MA-M (28-bit) and MA-S (36-bit). The table is bundled with iseeu.cc and divided by first byte, so your browser downloads only the slice covering your address and matches it locally; the address itself is never sent anywhere.

For each address you get the registered organization, the block size that matched, the two-letter country code from the registration address, and the address in colon, hyphen and Cisco dotted notation. The tool also flags a locally administered address, a multicast (group) address, and the broadcast address FF:FF:FF:FF:FF:FF.

How to use it

  1. Paste an address into the box. Colon (00:1A:2B:3C:4D:5E), hyphen (00-1A-2B-3C-4D-5E), Cisco dotted (001a.2b3c.4d5e) and bare hex (001A2B3C4D5E) all work, as do the first six hex digits alone.
  2. To check several devices at once, put one address per line.
  3. Read the result for each line: the registered organization, the block size (MA-L, MA-M or MA-S) and the country code.
  4. Check the flags, which explain why a randomized or multicast address has no manufacturer.
  5. Reuse the normalized address in whichever notation your router, switch or inventory sheet expects.

Six hex digits identify a 24-bit block, but an MA-M block needs seven and an MA-S block nine before it can be told apart from its neighbors, so paste the full address when you have it. Blocks assigned after the June 2026 snapshot will not be found. To collect addresses:

Windows    getmac /v          or   ipconfig /all
macOS      ifconfig en0 | grep ether
Linux      ip link show
Neighbors  arp -a  (Windows, macOS)     ip neigh  (Linux)

The macOS arp -a output drops leading zeros, printing 0:1a:2b:3c:4d:5e; restore the missing zero in each one-digit pair before pasting.

Use cases

  • An unnamed entry in your router's client list. Routers often show smart plugs, cameras and TV boxes as a bare MAC address with no hostname. The registered vendor narrows the field, and unplugging the likely suspect confirms it.
  • Reading a switch MAC table. Paste the addresses from show mac address-table one per line in their Cisco dotted form to see which ports have phones, printers or access points behind them.
  • Before adding a MAC filter or DHCP reservation. A locally administered flag means the device is using a private address, and a rule tied to it can stop matching when the device picks a new one.
  • Making sense of a packet capture. Destinations such as 01:00:5E:00:00:FB (IPv4 multicast DNS) or 33:33:00:00:00:01 (IPv6 all-nodes) are groups, not devices, and carry the multicast flag.
  • Virtual machines. Hypervisors generate addresses for virtual network cards. QEMU's default 52:54:00 prefix has the local bit set, so it is flagged rather than matched to a company.

How a MAC address is put together

A MAC address is six octets. In an MA-L block the first three octets identify the assignee, and the last three, a little over 16.7 million combinations, are theirs to hand out. MA-M and MA-S blocks are carved from larger blocks the IEEE keeps for the purpose: an MA-M fixes 28 bits and leaves 20 (1,048,576 addresses), an MA-S fixes 36 bits and leaves 12 (4,096).

MA-L   00:1A:2B | 3C:4D:5E    24-bit prefix, 24-bit device part
MA-M   00:1A:2B:3 | C:4D:5E   28-bit prefix, 20-bit device part
MA-S   00:1A:2B:3C:4 | D:5E   36-bit prefix, 12-bit device part

Two bits in the first octet carry special meaning. The lowest bit is the individual/group bit: 0 addresses a single interface, 1 addresses a multicast group. The next bit up is the universal/local bit: 0 means the address comes from an IEEE block, 1 means software set it locally and it belongs to no registered block. Both can be read from the second hex digit:

2nd hex digit   meaning
0 4 8 C         universal, unicast (ordinary hardware address)
2 6 A E         locally administered, unicast (often a randomized Wi-Fi address)
1 5 9 D         universal, multicast
3 7 B F         locally administered, multicast

Broadcast is the all-ones address that every station on the segment accepts; ARP requests and DHCP discovery messages use it. With every bit set it technically carries the group and local bits too, which is why it gets its own flag.

Private addresses, and why websites never see your MAC

Current iOS and Android releases replace the hardware address with a random one by default, usually different for each Wi-Fi network, and some devices also rotate it over time; Windows has a similar option. The random address has the local bit set, so it matches no manufacturer. It makes one phone harder to recognize across networks, but a MAC filter, parental-control rule or DHCP reservation on your router can stop working when the device switches addresses. For a fixed address on a network you trust, turn the private address setting off for that network only; Apple calls it Private Wi-Fi Address.

A MAC address only matters on the local link, the Wi-Fi network or Ethernet segment the device is attached to. Switches forward frames by MAC address; routers forward packets by IP address. When your traffic crosses a router it leaves in a new frame with the router's MAC as the source, so the next network sees the router, not you. A website receives your public IP address and your browser's headers, and no web API reveals the hardware address. The notable historical leak was IPv6 autoconfiguration with modified EUI-64, which copied the MAC into the address with the universal/local bit inverted:

MAC              00:1A:2B:3C:4D:5E
interface ID     021a:2bff:fe3c:4d5e    (FF:FE inserted, 0x02 bit inverted)

Current operating systems mostly use temporary or stable random interface identifiers instead (RFC 8981 and RFC 7217), so the IPv6 address a website sees normally reveals nothing about your hardware.

Frequently asked questions

Why does my phone's MAC address show no manufacturer?

Your phone is most likely using a private, randomized address for that Wi-Fi network. Such addresses have the locally administered bit set, meaning software generated them instead of taking them from an IEEE block, so no organization is on record and the tool flags the address instead. To see the real hardware address, check the device's About or status screen, or turn off the private address option for that one network.

Why is the organization a company I have never heard of?

The registry records whoever was assigned the address block, and that is often the maker of the Wi-Fi or Ethernet chip, a module supplier or a contract manufacturer rather than the brand on the box. A smart plug, a printer and a camera from three different brands can all show the same supplier. Treat the name as a clue and combine it with the hostname, the time the device joined and what is physically nearby.

Can a website see my MAC address?

No. A MAC address is used only within your local network segment. Each router along the path sends frames with its own MAC address, so by the time a request reaches a web server, only your public IP address and browser headers remain. Browsers provide no API for reading the hardware address. Older IPv6 setups that embedded the MAC in the address were the main exception, and modern systems avoid that.

What is the difference between an OUI and an MA-L?

MA-L, short for MAC Address Block Large, is the current IEEE name for the assignment people have long called an OUI: a 24-bit prefix with a little over 16.7 million addresses behind it. The 24-bit identifier itself is still called an OUI. MA-M and MA-S are smaller assignments with 28-bit and 36-bit prefixes, intended for organizations that need fewer addresses.

What does the country code tell me?

It comes from the postal address the organization gave the IEEE when the block was registered, so it shows where that company, or the office that filed the registration, was based at the time. It says nothing about where the device was built, sold or is located now. Companies move and get acquired while their blocks stay listed, so read it as a historical detail.

Is the address I paste sent to iseeu.cc?

No. The lookup table ships with the site, divided by the first byte of the address. Your browser fetches the small slice it needs from iseeu.cc and does the match locally, so the address itself is never sent anywhere. iseeu.cc keeps no request logs and no database of visitors, sets no cookies and shows no ads.

Can I find a device's owner or location from its MAC address?

Not from this registry. It records which organization was assigned a block of addresses, not who bought a particular device or where it is. On your own network, the router's client list or DHCP lease table ties each MAC address to an IP address and often a hostname, which is the practical way to track a device down. Beyond your local network segment, the address is not carried at all.

The registry records who was assigned an address block, not who made, sold or owns a particular device. Randomised addresses and blocks registered as private cannot be traced to a manufacturer.

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