Which company owns MAC address prefix 28:05:A5?

MAC address prefix 28:05:A5 is registered to Espressif Inc. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 28:05:A5 has a network interface built by Espressif Inc..

What is the OUI 28:05:A5?

28:05:A5 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Espressif Inc.. It covers every address from 28:05:A5:00:00:00 to 28:05:A5:FF:FF:FF, or 16,777,216 addresses in total. It is also written 28-05-A5.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in 28:05:A5:00:00:00 that is 28:05:A5 — 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 Espressif Inc. located?

Espressif Inc. is listed at Vistra Corporate Services Centre, Wickhams Cay II Road Town Tortola VG VG1110 in the IEEE OUI registry entry for 28:05:A5. This is the address the organization registered with the IEEE, which may differ from its current operating address.

How many MAC prefixes does Espressif Inc. own?

Espressif Inc. holds 339 OUI prefixes in the IEEE registry, of which 28:05:A5 is one. A device made by Espressif Inc. could carry a MAC address from any of them.

Espressif Inc.

MAC address prefix 28:05:A5 is registered to Espressif Inc. in the IEEE OUI registry. Any device whose MAC address begins with 28:05:A5 has a network interface built by Espressif 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 28:05:A5:00:00:00 to 28:05:A5:FF:FF:FF.

OUI prefix: 28:05:A5
Hyphen form: 28-05-A5
MAC range: 28:05:A5:00:00:00 – 28:05:A5:FF:FF:FF
Addresses in block: 16,777,216
Organization: Espressif Inc.
Address: Vistra Corporate Services Centre, Wickhams Cay II Road Town Tortola VG VG1110
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 Espressif Inc.

Espressif Inc. holds 339 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.

2025-08-23Assigned to "Espressif Inc."
archived source →
2026-07-17Assigned to "Espressif Inc."

Nearby in the registry

The prefixes assigned immediately before and after 28:05:A5:

FAQ

Which company owns MAC address prefix 28:05:A5?: MAC address prefix 28:05:A5 is registered to Espressif Inc. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 28:05:A5 has a network interface built by Espressif Inc..
What is the OUI 28:05:A5?: 28:05:A5 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Espressif Inc.. It covers every address from 28:05:A5:00:00:00 to 28:05:A5:FF:FF:FF, or 16,777,216 addresses in total. It is also written 28-05-A5.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in 28:05:A5:00:00:00 that is 28:05:A5 — 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 Espressif Inc. located?: Espressif Inc. is listed at Vistra Corporate Services Centre, Wickhams Cay II Road Town Tortola VG VG1110 in the IEEE OUI registry entry for 28:05:A5. This is the address the organization registered with the IEEE, which may differ from its current operating address.
How many MAC prefixes does Espressif Inc. own?: Espressif Inc. holds 339 OUI prefixes in the IEEE registry, of which 28:05:A5 is one. A device made by Espressif Inc. could carry a MAC address from any of them.