MAC Address Validator
Validate a MAC address and identify whether it is unicast or multicast, and universally or locally administered, from its address bits.
Last reviewed by the Radiatus Cloud team
Validate a MAC address and identify its unicast/multicast and universal/local properties.
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Validate and decode MAC addresses
A MAC address is more than just twelve hex digits: two bits in the first byte carry important meaning. This validator confirms that an address has the correct number of hexadecimal digits and then decodes those bits. The least significant bit of the first byte indicates whether the address is unicast, destined for one device, or multicast, destined for a group. The next bit indicates whether the address is universally administered, assigned by the manufacturer from its registered prefix, or locally administered, set by software or an administrator.
It also flags the special broadcast address of all ones and the all-zero address, and shows the first three bytes, the organisationally unique identifier that identifies the vendor.
Why these bits matter
Recognising a locally administered address is useful because randomised and virtual MAC addresses, increasingly common for privacy and in virtual machines, set the local bit. Distinguishing unicast from multicast helps when analysing traffic, since multicast frames are handled differently by switches. The organisationally unique identifier can be looked up to find the hardware vendor.
Understanding the structure of a MAC address helps network engineers interpret captures, troubleshoot address conflicts and recognise spoofed or randomised addresses. All validation happens locally in your browser.
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Frequently Asked Questions
What makes a MAC address valid?
It must contain exactly twelve hexadecimal digits, usually grouped by colons, hyphens or dots. The validator checks the digit count and the formatting.
What is the difference between unicast and multicast?
The lowest bit of the first byte decides this. If it is zero the frame targets one device; if it is one it targets a group of devices.
What does locally administered mean?
The second bit of the first byte indicates the address was set by software or an administrator rather than assigned by the manufacturer. Randomised and virtual MACs use this.
What is the OUI?
The organisationally unique identifier is the first three bytes of a universally administered MAC, registered to a specific hardware vendor and used to identify the maker.
How do I spot a randomised MAC?
Randomised privacy MAC addresses are locally administered and unicast, so a locally administered bit combined with a non-vendor prefix is a strong hint.
Privacy & Security
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How to Use
Enter a MAC address to validate it and reveal its properties.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.
Related Tools
Port Scanner
NetworkCheck which common ports respond on a host and understand what each exposed service means. Scan only systems you are authorised to test.
DNS Misconfiguration
NetworkAnalyze DNS records (TXT, SPF) for security gaps.
TLS Compat Tester
NetworkCheck client-server compatibility for TLS versions.