Which company owns MAC address prefix 8C:4D:B9?

MAC address prefix 8C:4D:B9 is registered to Unmonday Ltd in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 8C:4D:B9 has a network interface built by Unmonday Ltd.

What is the OUI 8C:4D:B9?

8C:4D:B9 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Unmonday Ltd. It covers every address from 8C:4D:B9:00:00:00 to 8C:4D:B9:FF:FF:FF, or 16,777,216 addresses in total. It is also written 8C-4D-B9.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in 8C:4D:B9:00:00:00 that is 8C:4D:B9 — 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 Unmonday Ltd located?

Unmonday Ltd is listed at Laivakatu 3 Helsinki Uusimaa FI 00150 in the IEEE OUI registry entry for 8C:4D:B9. This is the address the organization registered with the IEEE, which may differ from its current operating address.

Unmonday Ltd

MAC address prefix 8C:4D:B9 is registered to Unmonday Ltd in the IEEE OUI registry. Any device whose MAC address begins with 8C:4D:B9 has a network interface built by Unmonday Ltd. 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 8C:4D:B9:00:00:00 to 8C:4D:B9:FF:FF:FF.

OUI prefix: 8C:4D:B9
Hyphen form: 8C-4D-B9
MAC range: 8C:4D:B9:00:00:00 – 8C:4D:B9:FF:FF:FF
Addresses in block: 16,777,216
Organization: Unmonday Ltd
Address: Laivakatu 3 Helsinki Uusimaa FI 00150
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 "Unmonday Ltd"
archived source →
2026-07-17Assigned to "Unmonday Ltd"

Nearby in the registry

The prefixes assigned immediately before and after 8C:4D:B9:

FAQ

Which company owns MAC address prefix 8C:4D:B9?: MAC address prefix 8C:4D:B9 is registered to Unmonday Ltd in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 8C:4D:B9 has a network interface built by Unmonday Ltd.
What is the OUI 8C:4D:B9?: 8C:4D:B9 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Unmonday Ltd. It covers every address from 8C:4D:B9:00:00:00 to 8C:4D:B9:FF:FF:FF, or 16,777,216 addresses in total. It is also written 8C-4D-B9.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in 8C:4D:B9:00:00:00 that is 8C:4D:B9 — 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 Unmonday Ltd located?: Unmonday Ltd is listed at Laivakatu 3 Helsinki Uusimaa FI 00150 in the IEEE OUI registry entry for 8C:4D:B9. This is the address the organization registered with the IEEE, which may differ from its current operating address.