Which company owns MAC address prefix 04:AC:44?

MAC address prefix 04:AC:44 is registered to Holtek Semiconductor Inc. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 04:AC:44 has a network interface built by Holtek Semiconductor Inc..

What is the OUI 04:AC:44?

04:AC:44 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Holtek Semiconductor Inc.. It covers every address from 04:AC:44:00:00:00 to 04:AC:44:FF:FF:FF, or 16,777,216 addresses in total. It is also written 04-AC-44.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in 04:AC:44:00:00:00 that is 04:AC:44 — 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 Holtek Semiconductor Inc. located?

Holtek Semiconductor Inc. is listed at No.3, Creation Rd. II, Science Park Hsinchu TW 300 in the IEEE OUI registry entry for 04:AC:44. This is the address the organization registered with the IEEE, which may differ from its current operating address.

How many MAC prefixes does Holtek Semiconductor Inc. own?

Holtek Semiconductor Inc. holds 2 OUI prefixes in the IEEE registry, of which 04:AC:44 is one. A device made by Holtek Semiconductor Inc. could carry a MAC address from any of them.

Holtek Semiconductor Inc.

MAC address prefix 04:AC:44 is registered to Holtek Semiconductor Inc. in the IEEE OUI registry. Any device whose MAC address begins with 04:AC:44 has a network interface built by Holtek Semiconductor 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 04:AC:44:00:00:00 to 04:AC:44:FF:FF:FF.

OUI prefix: 04:AC:44
Hyphen form: 04-AC-44
MAC range: 04:AC:44:00:00:00 – 04:AC:44:FF:FF:FF
Addresses in block: 16,777,216
Organization: Holtek Semiconductor Inc.
Address: No.3, Creation Rd. II, Science Park Hsinchu TW 300
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.

Other prefixes from Holtek Semiconductor Inc.

Holtek Semiconductor Inc. holds 2 OUI prefixes in total. A device with this exact prefix could just as well carry any of these:

B8:CA:04

Assignment history (2)

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

2018-12-21Assigned to "Holtek Semiconductor Inc."
archived source →
2026-07-17Assigned to "Holtek Semiconductor Inc."

Nearby in the registry

The prefixes assigned immediately before and after 04:AC:44:

FAQ

Which company owns MAC address prefix 04:AC:44?: MAC address prefix 04:AC:44 is registered to Holtek Semiconductor Inc. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 04:AC:44 has a network interface built by Holtek Semiconductor Inc..
What is the OUI 04:AC:44?: 04:AC:44 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Holtek Semiconductor Inc.. It covers every address from 04:AC:44:00:00:00 to 04:AC:44:FF:FF:FF, or 16,777,216 addresses in total. It is also written 04-AC-44.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in 04:AC:44:00:00:00 that is 04:AC:44 — 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 Holtek Semiconductor Inc. located?: Holtek Semiconductor Inc. is listed at No.3, Creation Rd. II, Science Park Hsinchu TW 300 in the IEEE OUI registry entry for 04:AC:44. This is the address the organization registered with the IEEE, which may differ from its current operating address.
How many MAC prefixes does Holtek Semiconductor Inc. own?: Holtek Semiconductor Inc. holds 2 OUI prefixes in the IEEE registry, of which 04:AC:44 is one. A device made by Holtek Semiconductor Inc. could carry a MAC address from any of them.