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MAC Address Formatter

Developer Tools · Added

Cisco writes MAC addresses with dots, Linux with colons, Windows with hyphens, and half the vendor tools with nothing at all. Paste any of them to get every other form, plus what the first byte says about the address and the IPv6 link-local address it derives.

Colons, hyphens, Cisco dots or no separators at all — all four are read.

Try:

How to use the mac address formatter

  1. 1Paste a MAC address in any common notation.
  2. 2Copy whichever format the tool you are pasting into expects.
  3. 3Check the flags: whether the address is multicast, and whether it is vendor-assigned or locally administered.
  4. 4Take the EUI-64 or link-local form if you are working with IPv6.

Examples

Reformatting a vendor-assigned address

Input
3C:5A:B4:12:9F:0E
Result
Dot form 3c5a.b412.9f0e, bare 3c5ab4129f0e, OUI 3c:5a:b4, EUI-64 3e:5a:b4:ff:fe:12:9f:0e, link-local fe80::3e5a:b4ff:fe12:9f0e.

Neither flag bit is set, so this is a globally unique address from an IEEE-assigned block.

Spotting a randomised address

Input
A MAC seen on a wireless network whose first byte ends in 2, 6, A or E
Result
Reported as locally administered — the signature of the address randomisation phones and laptops now use by default, rather than a real hardware address.

About the mac address formatter

Four notations, one address

There is no technical difference between 3c:5a:b4:12:9f:0e, 3C-5A-B4-12-9F-0E, 3c5a.b412.9f0e and 3c5ab4129f0e. All four are the same six bytes, and the split is purely a matter of which vendor's tooling you grew up with — colons on Unix, hyphens on Windows, dotted quads of four hex digits on Cisco equipment.

The practical consequence is that comparing MAC addresses as strings is a bug waiting to happen. Two systems can hold the same address and disagree about it entirely, which is why normalising to one form before storing or matching is worth the small effort.

Why the sixth of the address space is not usable

A MAC address is 48 bits, but two of them are flags, so the usable space is smaller than it first appears — and one of those flags carves out the entire locally administered range for software to use freely.

That range has become far more important than it was. Address randomisation means a large share of the MAC addresses on any modern wireless network are locally administered and change between networks and over time. Anything that treats a MAC as a stable identifier for a device — access control lists keyed on it, DHCP reservations, licence enforcement — is building on ground that now moves by design.

Frequently asked questions

What do the two flag bits in the first byte mean?
The lowest bit marks a multicast address, meaning it is a group destination rather than one interface, and it is never set on a real source address. The next bit up marks a locally administered address — one assigned by software rather than drawn from a block the IEEE gave a manufacturer. Everything else in the first three bytes is the vendor's assigned prefix.
Does this look up which manufacturer made the device?
No, and that is deliberate. The OUI is shown so you can look it up, but shipping the IEEE registry would mean carrying roughly three megabytes of data into every page load to answer a question most visitors are not asking. The registry is public and searchable at the IEEE's own site.
How is the EUI-64 form derived?
The 48-bit address is split in the middle, the bytes ff and fe are inserted between the halves, and the locally-administered bit in the first byte is flipped. That last step catches people out constantly, because it changes the first octet — 3c becomes 3e here — and makes the derived address look like a different one entirely.
Why is the MAC address I see not the device's real one?
Modern phones and laptops randomise their wireless MAC per network by default, and generate a locally administered address to do it. It is a privacy measure: a stable hardware address broadcast constantly lets anyone within radio range track a device between locations. Any address with the locally administered bit set is a strong hint you are looking at a generated one.

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