Which company owns MAC address prefix C0:33:5E?

MAC address prefix C0:33:5E is registered to Microsoft in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with C0:33:5E has a network interface built by Microsoft.

What is the OUI C0:33:5E?

C0:33:5E is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Microsoft. It covers every address from C0:33:5E:00:00:00 to C0:33:5E:FF:FF:FF, or 16,777,216 addresses in total. It is also written C0-33-5E.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in C0:33:5E:00:00:00 that is C0:33:5E — 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 Microsoft located?

Microsoft is listed at 1 Microsoft Way Redmond Washington US 98052 in the IEEE OUI registry entry for C0:33:5E. This is the address the organization registered with the IEEE, which may differ from its current operating address.

How many MAC prefixes does Microsoft own?

Microsoft holds 9 OUI prefixes in the IEEE registry, of which C0:33:5E is one. A device made by Microsoft could carry a MAC address from any of them.

Microsoft

MAC address prefix C0:33:5E is registered to Microsoft in the IEEE OUI registry. Any device whose MAC address begins with C0:33:5E has a network interface built by Microsoft. 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 C0:33:5E:00:00:00 to C0:33:5E:FF:FF:FF.

OUI prefix: C0:33:5E
Hyphen form: C0-33-5E
MAC range: C0:33:5E:00:00:00 – C0:33:5E:FF:FF:FF
Addresses in block: 16,777,216
Organization: Microsoft
Address: 1 Microsoft Way Redmond Washington US 98052
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 Microsoft

Microsoft holds 9 OUI prefixes in total. A device with this exact prefix could just as well carry any of these:

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 "Microsoft"
archived source →
2026-07-17Assigned to "Microsoft"

Nearby in the registry

The prefixes assigned immediately before and after C0:33:5E:

FAQ

Which company owns MAC address prefix C0:33:5E?: MAC address prefix C0:33:5E is registered to Microsoft in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with C0:33:5E has a network interface built by Microsoft.
What is the OUI C0:33:5E?: C0:33:5E is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Microsoft. It covers every address from C0:33:5E:00:00:00 to C0:33:5E:FF:FF:FF, or 16,777,216 addresses in total. It is also written C0-33-5E.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in C0:33:5E:00:00:00 that is C0:33:5E — 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 Microsoft located?: Microsoft is listed at 1 Microsoft Way Redmond Washington US 98052 in the IEEE OUI registry entry for C0:33:5E. This is the address the organization registered with the IEEE, which may differ from its current operating address.
How many MAC prefixes does Microsoft own?: Microsoft holds 9 OUI prefixes in the IEEE registry, of which C0:33:5E is one. A device made by Microsoft could carry a MAC address from any of them.