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MAC Address Formatter & Validator

Paste MAC addresses in any common style to validate them and convert them to colon, hyphen, Cisco-dotted or plain 12-digit form.

Processed locally in your browser

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What is MAC Address Formatter & Validator?

A MAC (EUI-48) address is a 48-bit hardware identifier written as 12 hex digits, but vendors present it differently: AA:BB:CC:DD:EE:FF (Linux, macOS), AA-BB-CC-DD-EE-FF (Windows), aabb.ccdd.eeff (Cisco IOS) or aabbccddeeff (many databases). The tool accepts all of them, checks grouping and characters, and rewrites each address in every style.

It also validates the address and decodes two flag bits in the first byte: the I/G bit tells unicast from multicast/broadcast, and the U/L bit tells universally administered (burned-in) addresses from locally administered ones such as virtual or randomized MACs. No vendor (OUI) lookup is performed, because that would require a large external database.

How does it work?

  1. Paste one MAC address per line in any format.
  2. Choose the text output format and upper or lower case.
  3. Read the status (valid/invalid with reason) and the per-address details or table.
  4. Copy the normalized list into your switch config, DHCP reservation or spreadsheet.

Common use cases

  • Converting a Windows-style MAC list to the Cisco dotted notation used by switch ACLs and port security.
  • Validating MAC addresses exported from an inventory or DHCP lease file.
  • Spotting locally administered or multicast addresses that are unusual for a physical NIC.
  • Normalizing case and separators before de-duplicating or comparing addresses.

Examples

Try this input in the tool above:

Input
00:1A:2B:3C:4D:5E
aabb.ccdd.eeff
de-ad-be-ef-00-01
0a1b2c3d4e5f
Output
00:1A:2B:3C:4D:5E
AA:BB:CC:DD:EE:FF
DE:AD:BE:EF:00:01
0A:1B:2C:3D:4E:5F

Privacy

MAC Address Formatter & Validator runs entirely in your browser. The text or files you provide are processed on your device and are not uploaded, logged or stored on our servers.

Limitations

Only EUI-48 (12 hex digits) is supported, not EUI-64. The tool does not identify the manufacturer; a randomized or locally administered address cannot be traced to a vendor anyway.

Frequently asked questions

What is the Cisco MAC format?

Three groups of four hex digits separated by dots, e.g. aabb.ccdd.eeff, used by Cisco IOS.

How can I tell if a MAC is multicast?

Look at the least significant bit of the first byte: if it is 1 (for example 01:00:5E:…), the address is multicast; ff:ff:ff:ff:ff:ff is broadcast.

Does it show the vendor name?

No. Looking up the OUI needs a large registry that changes over time, so this tool intentionally works offline on structure only.

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