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MAC Address Validator

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Validate any MAC address instantly — supports colon, hyphen, and dot-separated formats. Detects multicast and locally administered bits. Free, client-side.

What is a MAC Address?

A MAC Address Validator checks whether a string is a correctly formatted MAC (Media Access Control) address. A MAC address is a 48-bit hardware identifier assigned to every network interface — Ethernet port, Wi-Fi card, Bluetooth adapter — by its manufacturer. It is used at the data link layer to uniquely identify devices within a local network segment. MAC addresses are represented as 12 hexadecimal digits, commonly written in one of four formats: colon-separated pairs (IEEE 802), hyphen-separated pairs (Windows), dot-separated groups of four (Cisco), or bare 12-digit hex without separators.

Beyond format checking, this validator also examines the first octet for two important flag bits. The least-significant bit (LSB) of the first octet indicates whether the address is unicast (0) or multicast (1). The second-least-significant bit indicates whether the address is globally unique (0, OUI-assigned) or locally administered (1, set by software). Both flags are reported in the validation result.

MAC address validation is relevant in several contexts: network configuration, device management systems, DHCP server administration, and debugging connectivity issues. When combined with the IP Address Validator, you can verify the full Layer 2 and Layer 3 addressing for a device.

How to use this MAC Address calculator

  1. Copy the MAC address from your device settings, network configuration, or system command output.
  2. Paste it into the MAC Address input field.
  3. The validator runs instantly — no button press needed.
  4. Check the Valid / Invalid badge.
  5. If valid, read the details: format style, unicast/multicast bit, and global/local bit.
  6. If invalid, check the digit count and separator style against the supported formats.

Formula & Methodology

A MAC address is 48 bits = 12 hexadecimal digits. Four separator formats are accepted:

| Format | Pattern | Example |
|---|---|---|
| IEEE colon | XX:XX:XX:XX:XX:XX | 00:1A:2B:3C:4D:5E |
| Windows hyphen | XX-XX-XX-XX-XX-XX | 00-1A-2B-3C-4D-5E |
| Cisco dot | XXXX.XXXX.XXXX | 001A.2B3C.4D5E |
| Bare hex | XXXXXXXXXXXX | 001A2B3C4D5E |

First-octet bit flags:
- Bit 0 (LSB): 0 = unicast, 1 = multicast
- Bit 1: 0 = globally unique (OUI assigned), 1 = locally administered

Valid example: 00:1A:2B:3C:4D:5E — colon-separated, unicast, OUI-assigned ✓

Invalid example: 00:1A:2B:3G:4D:5E — G is not a valid hexadecimal digit ✗
Frequently Asked Questions
What is a MAC address?
A MAC (Media Access Control) address is a unique hardware identifier assigned to a network interface card (NIC) by the manufacturer. It is used at the data link layer of the network stack to identify devices on a local network. Every Wi-Fi card, Ethernet port, and Bluetooth interface has its own MAC address.
What formats does this validator support?
The validator supports four common MAC address formats: colon-separated (00:1A:2B:3C:4D:5E, the IEEE 802 standard), hyphen-separated (00-1A-2B-3C-4D-5E, common on Windows), dot-separated in groups of four (001A.2B3C.4D5E, Cisco convention), and bare 12 hex digits with no separators (001A2B3C4D5E). Uppercase and lowercase hex digits are both accepted.
How many characters is a MAC address?
A MAC address is 48 bits, represented as 12 hexadecimal digits. With colon or hyphen separators (six pairs), the full string is 17 characters. In the Cisco dot-notation (three groups of four), it is 14 characters. Without any separators, it is 12 characters.
What is the OUI in a MAC address?
The first 24 bits (first 6 hex digits, or the first 3 octets) of a MAC address form the OUI (Organisationally Unique Identifier), assigned by the IEEE to device manufacturers. The OUI identifies the company that produced the network interface. The remaining 24 bits are the device's serial number assigned by the manufacturer.
What is a locally administered MAC address?
A locally administered address (LAA) has its second-least-significant bit of the first octet set to 1. This indicates the address was not assigned by the manufacturer — it was set manually or by software, such as when an operating system randomises the MAC address for privacy. Locally administered addresses are common in virtual machines, VPN adapters, and modern mobile devices using MAC randomisation.
What is MAC address randomisation and why does it affect validation?
Modern operating systems (iOS 14+, Android 10+, Windows 10) randomise the MAC address used when scanning for or connecting to Wi-Fi networks to prevent location tracking. A randomised MAC address is structurally valid (it passes all format checks) but has its LAA bit set and is not traceable to a real manufacturer. This validator detects the LAA bit and notes it in the result.
What is a multicast MAC address?
A multicast MAC address has its least-significant bit (LSB) of the first octet set to 1. It is used to send frames to a group of devices rather than a single device. The broadcast address (FF:FF:FF:FF:FF:FF) is the most well-known multicast address. Most devices have unicast addresses (LSB = 0). This validator reports whether the multicast bit is set.
Does this validator confirm a device is on a network or its manufacturer?
No. This tool checks format only — it confirms the MAC address is structurally valid (12 hex digits in a recognised separator format) and notes the unicast/multicast and global/local bits. It does not look up the OUI to identify the manufacturer, and it does not check whether the device is reachable. For OUI lookups, use the IEEE's public OUI database.
Is my MAC address stored when I validate it?
No. All validation runs entirely in your browser — nothing is sent to any server or stored. MAC addresses can reveal device manufacturers and network identifiers, so client-side processing is a firm requirement here.
Why does my MAC address show as locally administered?
If you are using a modern smartphone on Wi-Fi, the MAC address displayed may be a randomised privacy address with the LAA bit set. This is by design — your device generates a different random MAC for each network to prevent tracking. The address is still structurally valid; the LAA flag simply means it is not a manufacturer-assigned hardware address.
What is the difference between a MAC address and an IP address?
A MAC address identifies a physical network interface at the hardware level (Layer 2) and is fixed within a local network segment. An IP address is a logical address assigned by a router or DHCP server at the network level (Layer 3) and can change. MAC addresses are used for local delivery; IP addresses for routing across networks. Use the [IP Address Validator](/ip-address-validator/) to check IP format.

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