Which company owns MAC address prefix E4:DC:5F?

MAC address prefix E4:DC:5F is registered to Cofractal, Inc. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with E4:DC:5F has a network interface built by Cofractal, Inc..

What is the OUI E4:DC:5F?

E4:DC:5F is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Cofractal, Inc.. It covers every address from E4:DC:5F:00:00:00 to E4:DC:5F:FF:FF:FF, or 16,777,216 addresses in total. It is also written E4-DC-5F.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in E4:DC:5F:00:00:00 that is E4:DC:5F — 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 Cofractal, Inc. located?

Cofractal, Inc. is listed at 209 E Java Dr. #61593 Sunnyvale CA US 94089 in the IEEE OUI registry entry for E4:DC:5F. This is the address the organization registered with the IEEE, which may differ from its current operating address.

Cofractal, Inc.

MAC address prefix E4:DC:5F is registered to Cofractal, Inc. in the IEEE OUI registry. Any device whose MAC address begins with E4:DC:5F has a network interface built by Cofractal, Inc.. 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 E4:DC:5F:00:00:00 to E4:DC:5F:FF:FF:FF.

OUI prefix: E4:DC:5F
Hyphen form: E4-DC-5F
MAC range: E4:DC:5F:00:00:00 – E4:DC:5F:FF:FF:FF
Addresses in block: 16,777,216
Organization: Cofractal, Inc.
Address: 209 E Java Dr. #61593 Sunnyvale CA US 94089
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 (1)

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

2026-07-17Assigned to "Cofractal, Inc."

Nearby in the registry

The prefixes assigned immediately before and after E4:DC:5F:

FAQ

Which company owns MAC address prefix E4:DC:5F?: MAC address prefix E4:DC:5F is registered to Cofractal, Inc. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with E4:DC:5F has a network interface built by Cofractal, Inc..
What is the OUI E4:DC:5F?: E4:DC:5F is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Cofractal, Inc.. It covers every address from E4:DC:5F:00:00:00 to E4:DC:5F:FF:FF:FF, or 16,777,216 addresses in total. It is also written E4-DC-5F.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in E4:DC:5F:00:00:00 that is E4:DC:5F — 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 Cofractal, Inc. located?: Cofractal, Inc. is listed at 209 E Java Dr. #61593 Sunnyvale CA US 94089 in the IEEE OUI registry entry for E4:DC:5F. This is the address the organization registered with the IEEE, which may differ from its current operating address.