MAC Address Tool
Validate, reformat, and decode any MAC address in your browser, then derive its EUI-64 interface identifier and IPv6 link-local address.
Frequently Asked Questions
What format should a MAC address be in?
A MAC address is 48 bits, written as 6 octets (12 hexadecimal digits). The common formats are colon-separated (00:1A:2B:3C:4D:5E), hyphen-separated (00-1A-2B-3C-4D-5E), Cisco dot notation in three groups of four (001a.2b3c.4d5e), and bare with no separators (001A2B3C4D5E). All of these represent the same address, and case does not change the value, so uppercase and lowercase hex are equivalent.
What is the OUI in a MAC address?
The OUI, or Organizationally Unique Identifier, is the first 3 octets (the first 24 bits) of a MAC address, and it is assigned by the IEEE Registration Authority. The remaining 3 octets are assigned by the device manufacturer. Identifying which company owns an OUI requires the IEEE registry, which this tool does not include, so this tool shows you the OUI prefix and links to the IEEE registry rather than naming a vendor.
How do I know if a MAC address is unicast or multicast?
This is determined by the I/G bit, which is the least-significant bit of the first octet. If that bit is 0 the address is unicast, and if it is 1 the address is multicast. The all-ones address ff:ff:ff:ff:ff:ff is the broadcast address.
What is the difference between a universal and a locally administered MAC address?
This is determined by the U/L bit, which is the second-least-significant bit of the first octet. If that bit is 0 the address is universally administered, meaning it comes from an IEEE-assigned OUI, and if it is 1 the address is locally administered. Modern iOS and Android devices often generate locally administered, randomized MAC addresses per network for privacy.
How do you convert a MAC address to an IPv6 link-local address?
You derive an EUI-64 modified interface identifier and prepend the link-local prefix. Split the 48-bit MAC into two halves, insert FFFE in the middle to make a 64-bit value, then flip the U/L bit (the second-least-significant bit of the first octet). Prepend fe80::/64 to that interface identifier to form the IPv6 link-local address, as described in RFC 4291 and used by SLAAC in RFC 4862.