Which company owns MAC address prefix AC:91:5D?

MAC address prefix AC:91:5D is registered to Digital Control Technology Limited in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with AC:91:5D has a network interface built by Digital Control Technology Limited.

What is the OUI AC:91:5D?

AC:91:5D is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Digital Control Technology Limited. It covers every address from AC:91:5D:00:00:00 to AC:91:5D:FF:FF:FF, or 16,777,216 addresses in total. It is also written AC-91-5D.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in AC:91:5D:00:00:00 that is AC:91:5D — 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 Digital Control Technology Limited located?

Digital Control Technology Limited is listed at Unit 1805-06, 18/F, Hollywood Plaza, 610 Nathan Road, Mongkok, Kowloon, Hong Kong Hong Kong HK 00000 in the IEEE OUI registry entry for AC:91:5D. This is the address the organization registered with the IEEE, which may differ from its current operating address.

Digital Control Technology Limited

MAC address prefix AC:91:5D is registered to Digital Control Technology Limited in the IEEE OUI registry. Any device whose MAC address begins with AC:91:5D has a network interface built by Digital Control Technology Limited. 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 AC:91:5D:00:00:00 to AC:91:5D:FF:FF:FF.

OUI prefix: AC:91:5D
Hyphen form: AC-91-5D
MAC range: AC:91:5D:00:00:00 – AC:91:5D:FF:FF:FF
Addresses in block: 16,777,216
Organization: Digital Control Technology Limited
Address: Unit 1805-06, 18/F, Hollywood Plaza, 610 Nathan Road, Mongkok, Kowloon, Hong Kong Hong Kong HK 00000
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.

2025-05-13Assigned to "Digital Control Technology Limited"
archived source →
2026-07-17Assigned to "Digital Control Technology Limited"

Nearby in the registry

The prefixes assigned immediately before and after AC:91:5D:

FAQ

Which company owns MAC address prefix AC:91:5D?: MAC address prefix AC:91:5D is registered to Digital Control Technology Limited in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with AC:91:5D has a network interface built by Digital Control Technology Limited.
What is the OUI AC:91:5D?: AC:91:5D is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Digital Control Technology Limited. It covers every address from AC:91:5D:00:00:00 to AC:91:5D:FF:FF:FF, or 16,777,216 addresses in total. It is also written AC-91-5D.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in AC:91:5D:00:00:00 that is AC:91:5D — 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 Digital Control Technology Limited located?: Digital Control Technology Limited is listed at Unit 1805-06, 18/F, Hollywood Plaza, 610 Nathan Road, Mongkok, Kowloon, Hong Kong Hong Kong HK 00000 in the IEEE OUI registry entry for AC:91:5D. This is the address the organization registered with the IEEE, which may differ from its current operating address.