Which company owns MAC address prefix 00:04:CA?

MAC address prefix 00:04:CA is registered to FreeMs Corp. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 00:04:CA has a network interface built by FreeMs Corp..

What is the OUI 00:04:CA?

00:04:CA is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to FreeMs Corp.. It covers every address from 00:04:CA:00:00:00 to 00:04:CA:FF:FF:FF, or 16,777,216 addresses in total. It is also written 00-04-CA.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in 00:04:CA:00:00:00 that is 00:04:CA — and look that prefix up in the IEEE OUI registry. If the second-lowest bit of the first octet is set, the address is locally administered (a randomized or private MAC), which belongs to no manufacturer and will not resolve; modern phones and laptops use these by default on each network.

Where is FreeMs Corp. located?

FreeMs Corp. is listed at Shinhan Bldg. 6F, Seoul 150-736 KR KOREA in the IEEE OUI registry entry for 00:04:CA. This is the address the organization registered with the IEEE, which may differ from its current operating address.

FreeMs Corp.

MAC address prefix 00:04:CA is registered to FreeMs Corp. in the IEEE OUI registry. Any device whose MAC address begins with 00:04:CA has a network interface built by FreeMs Corp.. This prefix (the OUI, or Organizationally Unique Identifier) is assigned by the IEEE and is the first three octets of the address — it covers every MAC from 00:04:CA:00:00:00 to 00:04:CA:FF:FF:FF.

OUI prefix: 00:04:CA
Hyphen form: 00-04-CA
MAC range: 00:04:CA:00:00:00 – 00:04:CA:FF:FF:FF
Addresses in block: 16,777,216
Organization: FreeMs Corp.
Address: Shinhan Bldg. 6F, Seoul 150-736 KR KOREA
Source: IEEE OUI registry

Have a full MAC address? Look it up— we'll also tell you if it's a randomized (private) address rather than a real manufacturer prefix.

Assignment history (2)

The IEEE registry publishes current state only — this is the change record we've kept since we started tracking it daily.

2016-07-29Assigned to "FreeMs Corp."
archived source →
2026-07-17Assigned to "FreeMs Corp."

Nearby in the registry

The prefixes assigned immediately before and after 00:04:CA:

FAQ

Which company owns MAC address prefix 00:04:CA?: MAC address prefix 00:04:CA is registered to FreeMs Corp. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 00:04:CA has a network interface built by FreeMs Corp..
What is the OUI 00:04:CA?: 00:04:CA is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to FreeMs Corp.. It covers every address from 00:04:CA:00:00:00 to 00:04:CA:FF:FF:FF, or 16,777,216 addresses in total. It is also written 00-04-CA.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in 00:04:CA:00:00:00 that is 00:04:CA — and look that prefix up in the IEEE OUI registry. If the second-lowest bit of the first octet is set, the address is locally administered (a randomized or private MAC), which belongs to no manufacturer and will not resolve; modern phones and laptops use these by default on each network.
Where is FreeMs Corp. located?: FreeMs Corp. is listed at Shinhan Bldg. 6F, Seoul 150-736 KR KOREA in the IEEE OUI registry entry for 00:04:CA. This is the address the organization registered with the IEEE, which may differ from its current operating address.