MAC Address Formatter

Paste a MAC address in any punctuation and get it back in all four common forms: colon-separated (00:1a:2b:3c:4d:5e), hyphen-separated, Cisco's four-digit dotted groups (001a.2b3c.4d5e) and bare with no separators, with a switch for upper or lower case. Each row copies on its own, which is the point — the form a tool wants is rarely the form you have.

The parser throws away every character that is not a hex digit and then insists on exactly twelve. That accepts anything with the right digits in the right order, including mixed or absent separators, but it also means stray hex letters in the surrounding text are counted: paste MAC=001a2b3c4d5e and the a and c of the label push the count to fourteen, so it is rejected rather than silently misread. Trim the label and it parses.

Below the formats, two bits of the first octet are decoded, and they are the two that decide what the address means. The low bit is the I/G bit: set means the frame is multicast, so ff:ff:ff:ff:ff:ff reads as multicast rather than as a device. The next bit up is the U/L bit: set means the address is locally administered rather than assigned from a manufacturer's OUI. That is what makes the second hex digit of a randomised address always one of 2, 6, a or e — the four values with the U/L bit set and the I/G bit clear — which is how a phone's private Wi-Fi address announces itself. It is also why de:ad:be:ef:00:01, a favourite in documentation, is technically a locally administered unicast address: 0xde has that bit set.

Nothing is looked up or sent anywhere; the vendor behind an OUI is a separate question this tool does not answer.