BYTETOOLS

MAC Address Formatter

Convert MAC addresses between colon, hyphen, Cisco dotted and bare-hex notation in bulk, with case control and U/L + multicast bit decoding. 100% in-browser.

Reformatted (1 address)

00:1a:2b:3c:4d:5e
Universal (vendor-assigned)
Administration (U/L bit)
Unicast
Transmission (I/G bit)

Structure of 00:1a:2b:3c:4d:5e

OUI (vendor part): 00:1A:2B · NIC (device part): 3C:4D:5E

The two low bits of the first octet (0x00) carry meaning: bit 0 = multicast, bit 1 = locally administered. Randomized privacy MACs on phones always set the locally-administered bit.

What is the MAC Address Formatter?

The MAC Address Formatter converts hardware addresses between every common notation: colon-separated (aa:bb:cc:dd:ee:ff), Windows-style hyphens (aa-bb-cc-dd-ee-ff), Cisco dotted triplets (aabb.

  • Converts between colon, hyphen, Cisco dotted-triplet and bare-hex formats
  • Bulk mode — reformat a whole list in one go
  • Uppercase or lowercase output
  • Decodes the locally-administered (U/L) and multicast (I/G) bits of the first octet
  • Splits the OUI vendor part from the NIC device part
  • Strict 12-hex-digit validation with per-line error reporting

How to use the MAC Address Formatter

  1. 1

    Paste one or more MAC addresses, one per line, in any common notation.

  2. 2

    Pick the output format: colon, hyphen, Cisco dotted or bare hex.

  3. 3

    Choose uppercase or lowercase output.

  4. 4

    Copy the reformatted list, and check the U/L and multicast bit decoding below it.

About the MAC Address Formatter

The MAC Address Formatter converts hardware addresses between every common notation: colon-separated (aa:bb:cc:dd:ee:ff), Windows-style hyphens (aa-bb-cc-dd-ee-ff), Cisco dotted triplets (aabb.ccdd.eeff) and bare hex — in uppercase or lowercase, one address or a whole list at a time.

It also decodes what the first octet actually says about an address: whether it is universally administered (burned in by the vendor) or locally administered (like the randomized MACs modern phones use), and whether it is unicast or multicast. The OUI vendor half and device half are split out visually.

Validation is strict — exactly 12 hex digits — and invalid lines are reported, not guessed at. Everything runs 100% locally in your browser; MAC addresses identify hardware on your network, and they never leave your machine here.

Frequently asked questions

What are the different MAC address formats?

The same 48-bit address is written differently by different systems: Linux and macOS use colons (aa:bb:cc:dd:ee:ff), Windows uses hyphens (AA-BB-CC-DD-EE-FF), and Cisco IOS uses three dot-separated groups of four (aabb.ccdd.eeff). They are interchangeable — only the separators and case differ.

What does a locally administered MAC address mean?

If bit 1 of the first octet is set (second hex digit is 2, 6, A or E), the address was assigned by software rather than burned in by the manufacturer. Randomized privacy MACs on iOS and Android, many VMs and some container platforms all use locally administered addresses.

How can I tell if a MAC address is multicast?

Check the lowest bit of the first octet: if it is 1 (first octet odd), frames to that address go to a group of devices rather than one. Real device NICs always have unicast addresses, so a multicast source MAC in a capture usually indicates something odd.

Can this tool tell me the vendor of a MAC address?

It separates the OUI — the first three octets, which identify the vendor — but does not look up the vendor name. The IEEE OUI registry is a multi-megabyte database that changes constantly, and this tool deliberately works fully offline with no lookups.

Are the MAC addresses I paste uploaded anywhere?

No. Formatting and bit decoding run entirely in your browser with JavaScript. MAC addresses can identify your hardware and network, so nothing is transmitted, logged or stored by this tool.

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