Which company owns MAC address prefix 04:65:65?

MAC address prefix 04:65:65 is registered to Testop in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 04:65:65 has a network interface built by Testop.

What is the OUI 04:65:65?

04:65:65 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Testop. It covers every address from 04:65:65:00:00:00 to 04:65:65:FF:FF:FF, or 16,777,216 addresses in total. It is also written 04-65-65.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in 04:65:65:00:00:00 that is 04:65:65 — 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 Testop located?

Testop is listed at 808, Hanshin IT tower, 272 digital-ro Guro-gu Seoul KR KS013 in the IEEE OUI registry entry for 04:65:65. This is the address the organization registered with the IEEE, which may differ from its current operating address.

Testop

MAC address prefix 04:65:65 is registered to Testop in the IEEE OUI registry. Any device whose MAC address begins with 04:65:65 has a network interface built by Testop. 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 04:65:65:00:00:00 to 04:65:65:FF:FF:FF.

OUI prefix: 04:65:65
Hyphen form: 04-65-65
MAC range: 04:65:65:00:00:00 – 04:65:65:FF:FF:FF
Addresses in block: 16,777,216
Organization: Testop
Address: 808, Hanshin IT tower, 272 digital-ro Guro-gu Seoul KR KS013
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 "Testop"
archived source →
2026-07-17Assigned to "Testop"

Nearby in the registry

The prefixes assigned immediately before and after 04:65:65:

FAQ

Which company owns MAC address prefix 04:65:65?: MAC address prefix 04:65:65 is registered to Testop in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 04:65:65 has a network interface built by Testop.
What is the OUI 04:65:65?: 04:65:65 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Testop. It covers every address from 04:65:65:00:00:00 to 04:65:65:FF:FF:FF, or 16,777,216 addresses in total. It is also written 04-65-65.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in 04:65:65:00:00:00 that is 04:65:65 — 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 Testop located?: Testop is listed at 808, Hanshin IT tower, 272 digital-ro Guro-gu Seoul KR KS013 in the IEEE OUI registry entry for 04:65:65. This is the address the organization registered with the IEEE, which may differ from its current operating address.