MAC / OUI Vendor Lookup

MAC / OUI Vendor Lookup

Every network interface's MAC address is a 48-bit identifier, and the first half historically identified the manufacturer: the IEEE Registration Authority assigns a 24-bit prefix — the Organizationally Unique Identifier (OUI), now formally called an MA-L ("MAC Address Block Large") assignment — to each vendor, who then numbers its own devices within the remaining 24 bits. As MA-L blocks (16.7 million addresses each) became too large for organizations that only needed a handful, IEEE introduced two smaller registries: MA-M ("Medium", a 28-bit prefix, about 1 million addresses) and MA-S ("Small", a 36-bit prefix, about 65,000 addresses). This tool checks all three and returns the most specific match — an MA-S assignment nested inside a vendor's own broader MA-L block always wins.

Two bits in the very first byte of any MAC address are set aside for local administration, independent of the OUI table. The U/L bit marks whether the address was assigned by IEEE (universally administered) or set locally — by an administrator, a virtualization hypervisor, or, increasingly, by your operating system itself: modern Windows, Android, iOS and Linux all randomize the MAC address a device presents to each Wi-Fi network by default, specifically to stop a device being tracked across networks by its hardware address, and every randomized address has this bit set. When it's set, this tool intentionally does NOT search the OUI table at all — a locally-administered address is by definition not an IEEE-issued OUI, so a lookup would return nothing meaningful. You'll see an explicit note instead of a vendor name; that's the tool working correctly, not a broken table. The other bit, I/G, simply reports whether the address is a normal unicast address or a multicast/broadcast one, independent of the U/L bit.

You can also search the other direction: type a manufacturer's name, or part of one (like "cisco" or "apple"), to get every OUI range IEEE has on record for it — case-insensitive, matched as a substring. Results are capped at 50 rows per search; most vendors hold far fewer OUI blocks than that, but a handful of large manufacturers with hundreds of registered ranges will show a truncation notice, and narrowing the search term returns a tighter set.

The registry data ships embedded in this service's own binary, regenerated from the IEEE Registration Authority's public MA-L/MA-M/MA-S listings ahead of each release rather than fetched live on every request — so a lookup here never depends on IEEE's own servers being reachable, and never sends your query anywhere but our own API.

Data provided by the IEEE Registration Authority.

How to use this lookup

1. Enter a MAC address or vendor name

   Type a MAC address in any notation (AA:BB:CC:11:22:33, AA-BB-CC-11-22-33, aabb.cc11.2233 or AABBCC112233), or a manufacturer name like "cisco" to search the other direction.

2. Look up

   Click "Look up" (or open a permalink URL) to check the address or name against the embedded IEEE MA-L/MA-M/MA-S registries.

3. Read the result

   For a MAC address you get the normalized form, the U/L and I/G bits, and the vendor (when it's an IEEE-assigned address that matches our registry); for a vendor name you get every matching OUI range.

4. Share

   The page URL updates with your query as a permalink, so you can copy and share the current result directly.

Glossary

OUI

Organizationally Unique Identifier — the historical name for a 24-bit vendor prefix IEEE assigns; the current formal name for this size of assignment is MA-L.

MA-L

"MAC Address Block Large" — a 24-bit prefix (16.7 million addresses), the modern name for what used to be called simply an OUI assignment.

MA-M

"MAC Address Block Medium" — a 28-bit prefix (about 1 million addresses), for organizations that don't need a full MA-L block.

MA-S

"MAC Address Block Small" — a 36-bit prefix (about 65,000 addresses), the smallest IEEE MAC-address-block assignment.

U/L bit

Universal/Local bit — the second-least-significant bit of a MAC address's first byte. 0 means IEEE-assigned (universally administered); 1 means locally administered — set locally, or by MAC randomization.

I/G bit

Individual/Group bit — the least-significant bit of a MAC address's first byte. 0 means a normal unicast address; 1 means multicast or broadcast.

MAC randomization

A privacy feature in modern operating systems that presents a different, locally-administered MAC address to each Wi-Fi network instead of the device's real, IEEE-assigned hardware address, to prevent tracking across networks.

API equivalent

This page calls our own public tools endpoint under the hood — you can call the same endpoint directly, unauthenticated, subject to a per-caller rate limit:

curl "https://ip.xakki.pro/api/v1/tools/mac?q=AA:BB:CC:11:22:33"

Example response:

{
  "query": "AA:BB:CC:11:22:33",
  "queryType": "mac",
  "mac": "AA:BB:CC:11:22:33",
  "isLocallyAdministered": false,
  "isMulticast": false,
  "vendor": {"name": "Example Corp", "block": "MA-L", "prefix": "AA:BB:CC/24"}
}

Example response for a locally-administered address:

{
  "query": "02:11:22:33:44:55",
  "queryType": "mac",
  "mac": "02:11:22:33:44:55",
  "isLocallyAdministered": true,
  "isMulticast": false,
  "vendor": null,
  "note": "This MAC is locally administered (U/L bit set): it is a randomized or manually assigned address, not an IEEE-issued OUI, so vendor lookup does not apply."
}

Read the full API docs

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Frequently asked questions

What's the difference between MA-L, MA-M and MA-S?

They're all IEEE MAC-address-block registries, differing only in size: MA-L (formerly just "OUI") assigns a 24-bit prefix (16.7 million addresses), MA-M a 28-bit prefix (about 1 million), and MA-S a 36-bit prefix (about 65,000) — for organizations that need far fewer addresses than a full MA-L block. When ranges overlap, the most specific (smallest) block wins.

Why does my MAC address show no vendor, just a note about local administration?

Because its U/L bit is set — it's a locally-administered address, not an IEEE-issued OUI. This is common: virtual machines, some Bluetooth devices, and — increasingly — modern operating systems doing MAC randomization on Wi-Fi all generate addresses with this bit set. Since such an address was never assigned by IEEE, looking it up in the OUI table would be meaningless, so this tool skips the lookup entirely and tells you why rather than returning a misleading "not found".

Can I search by vendor name instead of a MAC address?

Yes — type any part of a manufacturer's name (case-insensitive) and this tool searches every OUI range IEEE has on record for a match, up to 50 results per search.

Does this tool query IEEE live, or use cached data?

Neither, really — the registry is embedded directly in this service and regenerated from IEEE's public listings ahead of each release, not fetched live per request and not cached with an expiry. It's as current as our last release, which is more than sufficient for a slowly-changing reference registry.

Does this tool log or store the addresses I look up?

Your query is sent to our server to check it against the embedded registry (unlike our purely client-side calculators), but the lookup itself never leaves this service — there's no third-party IEEE call to make on your behalf, and no permanent record tied to you.

Is there a rate limit on this tool?

Yes — this page and its underlying API endpoint share the free tools lane's per-caller rate limit, independent of our main IP lookup API's daily quota. If you need higher volume or programmatic access, our API docs cover the paid tiers.