MAC Address Formatter
Any notation in. Separators are ignored, only the 12 hex digits matter.
00:1b:44:11:3a:b7
- 00:1B:44
- OUI (first 3 bytes)
- Globally unique
- Administration
- Unicast
- Destination
00:1b:44:11:3a:b700:1B:44:11:3A:B700-1B-44-11-3A-B7001b.4411.3ab7001b44113ab7The MAC address formatter converts between the five notations different systems use and reports what the address itself says: its manufacturer prefix, and whether it is globally unique or locally administered. Input can be in any notation, only the twelve hexadecimal digits matter.
How it works
A MAC address is six bytes. Every notation is the same twelve hex digits with different separators, which is why converting is purely cosmetic, but tools that parse only one form are a common source of bugs.
- Colon-separated lowercase: Linux and macOS.
- Hyphen-separated uppercase: Windows, including ipconfig output.
- Dotted quads of four digits: Cisco equipment.
- No separators: many APIs and log formats.
Two bits in the first byte carry meaning. The least significant marks a multicast address; the next marks a locally administered one that no manufacturer owns. A locally administered address always has 2, 6, A or E as its second hex digit.
Examples
Windows to Linux notation
Address
00-1B-44-11-3A-B7
Result
00:1b:44:11:3a:b7 · OUI 00:1B:44 · globally unique · unicast
The first three bytes are the manufacturer prefix, registered with the IEEE. The first byte is even, so this is a unicast address.
A locally administered address
Address
9a3fc108d744
Result
Reported as locally administered
The second hex digit of the first byte is a, which sets the local bit. This is what a randomised or manually assigned address looks like.
Frequently asked questions
What does the OUI tell me?
The first three bytes are the Organisationally Unique Identifier, registered with the IEEE to a manufacturer. Looking it up in the IEEE registry identifies who made the network interface. That only holds for globally unique addresses. A locally administered one has no registered owner.
How do I tell a randomised MAC address from a real one?
By the second hex digit of the first byte. If it is 2, 6, A or E, the local bit is set and the address was assigned locally rather than by a manufacturer. Phones use exactly this when randomising their MAC for Wi-Fi privacy.
Why do so many notations exist?
Because different vendors standardised independently before any convention settled. Cisco grouped four digits, Windows chose hyphens and uppercase, Unix chose colons and lowercase. All describe the same six bytes, and software that accepts only one form breaks on input from another.
What is the difference between this and the random MAC generator?
That one produces new addresses for test data. This one takes an address you already have and converts or inspects it, which is what you need when reconciling output from two different tools.