UsefulTab
MAC Address Tool
Generate MACs; sample vendor lookup.
Generate locally-administered MACs
Pick casing, separator, and count — and optionally a custom prefix — then generate valid, self-assigned MAC addresses, each with its own copy button. A small sample vendor lookup is on the left.
Runs entirely in your browserGenerate MAC addresses and look up a sample vendor
Generate random MAC addresses that are valid and locally administered — the first octet is marked as locally-administered unicast, the range meant for self-assigned addresses, so they will not collide with a real manufacturer's burned-in address. Choose upper or lower case, the separator (colon, hyphen, Cisco-style dots, or none), how many to generate, and an optional custom prefix to pin the leading octets. Every address uses the Web Crypto random generator. The tool also offers an OUI vendor lookup, but it is honest about its limits: it ships only a small built-in sample of about fifteen well-known prefixes (Apple, Cisco, Intel, VMware, Raspberry Pi and a few more) and makes no network calls, so it is a convenience, not the full IEEE registry. Everything runs in your browser and nothing is uploaded.
Common questions
What makes a generated MAC locally administered?
When no custom prefix is set, the tool forces the first octet's low two bits to b10 — the locally-administered bit is set and the multicast/group bit is cleared. That marks the address as a self-assigned unicast MAC, the range intended for addresses you make up yourself rather than a vendor's assigned block.
What separators and casing can I choose?
Colon (00:1A:2B:…), hyphen (00-1A-2B-…), Cisco-style dotted groups of four (001a.2b3c.4d5e), or no separator at all, each in upper or lower case. Pick whichever your switch, config file, or script expects.
How complete is the vendor lookup?
Deliberately small. It matches only against a built-in sample of roughly fifteen well-known OUI prefixes and makes no network request, so a real address will often say “not in the sample.” For a definitive vendor, consult the official IEEE OUI registry — this lookup is a quick convenience, not a replacement for it.
Can I generate many at once with a fixed prefix?
Yes. Set a custom prefix (one to six octets, any separator) to pin the leading octets, choose a count, and generate — the remaining octets are filled randomly. This is handy for seeding a lab or test fixture with addresses under one prefix.
Is anything uploaded or looked up online?
No. Generation uses the local Web Crypto random source and the vendor lookup reads a map built into the page. There are no network calls, so the tool works entirely offline and nothing you enter leaves your browser.