MAC Address Analyzer
Validate an EUI-48 MAC address, get its four notations and interpret its I/G and U/L bits. Local analysis, nothing sent.
A local analysis of an address format: it identifies no manufacturer or device and cannot confirm real uniqueness on a network.
Input
Enable JavaScript for local analysis. The guide remains accessible.
Results
Enter a complete MAC address or choose an example.
- Normalized form
- Entered notation
- ColonHyphenCisco (dot)Compact
Type (I/G bit)
Individual (unicast): I/G = 0, intended for one interface.
Group: I/G = 1, intended for a set of interfaces (multicast). Broadcast is only one case.
Administration (U/L bit)
Universal: U/L = 0, the form reserved for identifiers assigned through the IEEE. No registry is consulted.
Local: U/L = 1, a locally defined value (administrator, software, virtualization, random address…).
Special case
None
Null address: every bit is 0. Often used by software as a missing or unconfigured value; the tool does not treat it as identifying an interface.
Broadcast: every bit is 1. A group address for all stations on the local network; U/L = 1 does not indicate local assignment here.
| Weight | Bit | Role |
|---|---|---|
| 128 | — | |
| 64 | — | |
| 32 | — | |
| 16 | — | |
| 8 | — | |
| 4 | — | |
| 2 | U/L | |
| 1 | I/G |
These bits describe a format convention. Software can configure any value: they prove neither authenticity, origin nor that a device exists.
Understanding a MAC address
An EUI-48 MAC address has 48 bits, written as 12 hexadecimal digits. Colon, hyphen, Cisco and compact notations represent the same value; letter case does not matter. The normalized form uses colons and upper case.
The first octet carries two bits defined by IEEE 802 (summarized in RFC 9542). The weight-1 bit, rightmost in binary, is I/G: 0 individual, 1 group. The weight-2 bit is U/L: 0 universally administered, 1 locally administered. Ethernet sends each octet least significant bit first, so I/G is the first bit transmitted.
Examples: 01:00:5E:00:00:01 is a universal group address (IPv4 multicast); 33:33:00:00:00:01 a local group address (IPv6 multicast); 02:00:00:00:00:01 a local individual address. FF:FF:FF:FF:FF:FF is broadcast, one particular group.
The tool does not identify manufacturers, query registries, detect devices or verify uniqueness. Software can change a universal address; the bits do not prove origin. EUI-64 is not supported.
Analysis runs in the browser; the tool sends and stores nothing. The clipboard and extensions can expose copied values.
Frequently asked questions
Is a group address a broadcast?
Not necessarily. I/G = 1 indicates a group (multicast) address. Broadcast FF:FF:FF:FF:FF:FF is only one such group: all stations.
Is a locally administered address suspicious?
No. Virtual machines, containers and random privacy addresses commonly use U/L = 1. Conversely, U/L = 0 does not guarantee an original address.
Why is no manufacturer shown?
That would require an up-to-date IEEE registry, and a prefix assignment does not establish which device actually uses the address. The tool is limited to the format.