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MAC Address Validator

Check a list of MAC addresses line by line and see whether each is valid, why not, and what kind of address it is.

Processed locally in your browser

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0 chars · 0 lines
The result will appear here.

What is MAC Address Validator?

A MAC address identifies a network interface. EUI-48 has 6 bytes (12 hex digits) and EUI-64 has 8 bytes (16 digits). They are written many ways: AA:BB:CC:DD:EE:FF, AA-BB-CC-DD-EE-FF, aabb.ccdd.eeff (Cisco), AABBCC-DDEEFF or AABBCCDDEEFF.

This validator accepts all of these, rejects mixed separators, wrong lengths, bad groupings and non-hex characters, and gives a reason for each failure. For valid addresses it reads the two low bits of the first byte: I/G (unicast or multicast group) and U/L (universally or locally administered). It also flags broadcast, all-zero and FF:FE-expanded addresses, counts duplicates and returns a summary and a CSV.

How does it work?

  1. Paste one MAC address per line, in any common notation.
  2. Choose whether to accept EUI-48 and EUI-64, or only one of them, and whether the no-separator form is allowed.
  3. Read the status banner and the summary, then the table: valid or invalid, canonical form, transmission and administration type.
  4. Copy or download the CSV to reuse the results.

Common use cases

  • Cleaning an inventory or DHCP export before importing it into a CMDB.
  • Checking a whitelist or ACL for typos such as a missing digit or a stray character.
  • Finding locally administered addresses, as used by virtual machines, containers and randomised phone MACs.
  • Telling multicast group addresses such as 01:00:5E:… from normal device addresses.

Examples

Try this input in the tool above:

Input
00:1A:2B:3C:4D:5E
00-1A-2B-3C-4D-5F
001a.2b3c.4d60
01:00:5E:00:00:FB
02:42:AC:11:00:02
00:1A:2B:FF:FE:3C:4D:5E
GG:1A:2B:3C:4D:5E
00:1A:2B:3C:4D
Output
line,input,valid,standard,notation,canonical,transmission,administration,note
1,00:1A:2B:3C:4D:5E,true,EUI-48,colon,00:1a:2b:3c:4d:5e,unicast,universal,
2,00-1A-2B-3C-4D-5F,true,EUI-48,hyphen,00:1a:2b:3c:4d:5f,unicast,universal,
3,001a.2b3c.4d60,true,EUI-48,dot4,00:1a:2b:3c:4d:60,unicast,universal,
4,01:00:5E:00:00:FB,true,EUI-48,colon,01:00:5e:00:00:fb,multicast,universal,
5,02:42:AC:11:00:02,true,EUI-48,colon,02:42:ac:11:00:02,unicast,local,
6,00:1A:2B:FF:FE:3C:4D:5E,true,EUI-64,colon,00:1a:2b:ff:fe:3c:4d:5e,unicast,universal,FF:FE in the middle: an EUI-48 expanded to EUI-64
7,GG:1A:2B:3C:4D:5E,false,,,,,,"contains a character that is not hexadecimal or a separator (""G"")"
8,00:1A:2B:3C:4
…

Privacy

MAC Address 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

Validation checks structure only. It does not look up the vendor (OUI), and a well-formed address does not prove that a real device uses it.

Frequently asked questions

What do the I/G and U/L bits mean?

They are the two lowest bits of the first byte. I/G = 1 marks a multicast (group) address, and U/L = 1 marks a locally administered address that was not assigned by the manufacturer.

Is 00:00:00:00:00:00 valid?

It is well formed, so it counts as valid, but the tool flags it as an all-zero address that cannot identify a real device. FF:FF:FF:FF:FF:FF is flagged as the broadcast address.

How is this different from the MAC address formatter?

The formatter converts each address into every notation. The validator focuses on checking: reasons for failures, EUI-48 versus EUI-64, address bits, duplicates and an aggregated summary.

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