Generate random MAC addresses with custom OUI, bits and format

MACs are generated locally with the browser's RNG — nothing is uploaded.

🎲 MAC Address Generator — Free Online Tool

Generate random MAC addresses, free. A MAC address is a 48-bit hardware identifier whose two low bits of the first byte flag whether it's unicast or multicast and universally or locally administered. This generator creates one or many random MAC addresses with control over those bits, an optional custom OUI prefix and the output format — entirely in your browser using its built-in random number generator.

🚀 Why use this MAC Address Generator tool?

It produces valid, correctly-flagged MAC addresses — locally-administered and unicast by default — so they're safe to assign to virtual interfaces, lab gear or test fixtures without colliding with a real vendor's OUI. 100% free, no registration, and complete privacy — everything runs locally in your browser, so your data never touches a server.

Key Features

🎲Single or bulk

Generate one MAC or up to 100 at once for seeding lab devices, virtual NICs or test data.

🚩Correct flags

Defaults to locally-administered + unicast so generated addresses don't impersonate a real OUI or look like a multicast group.

🏷️Custom OUI & format

Pin a specific OUI prefix and choose colon, hyphen or Cisco-dotted output in upper or lower case.

🔒100% private

Addresses are generated locally with the browser's RNG; nothing is uploaded or stored.

Popular Use Cases

Virtualisation

  • Assign VM/NIC MACs
  • Avoid OUI collisions
  • Seed lab hypervisors

Testing

  • Generate fixtures
  • Bulk test data
  • Unique device IDs for tests

Learning

  • See the U/L and I/G bits
  • Experiment with formats
  • Teach MAC structure

What It Handles

Generates

  • Single or up to 100
  • Custom OUI prefix
  • Flagged correctly

Format

  • Colon / hyphen / Cisco
  • Upper or lower case
  • Copy all

Privacy

  • Browser RNG
  • No network calls
  • Runs offline

Related Tools

Sources & References

Frequently Asked Questions

Are these MAC addresses valid?

Yes. They are well-formed 48-bit addresses. By default they are flagged locally-administered and unicast, which is exactly what you want for virtual interfaces and test devices so they don't clash with a real vendor OUI.

Should I use locally-administered addresses?

For anything you make up yourself — VMs, containers, lab gear — yes. The locally-administered bit signals the address isn't a burned-in OUI, which is the correct, collision-safe choice. Leave it on unless you have a specific reason to mimic a real OUI.

Can I generate MACs for a specific vendor?

Enter that vendor's OUI as the custom prefix and the first three bytes will be fixed to it while the rest are random. Use real OUIs only for legitimate testing.

What's the difference between unicast and multicast here?

Unicast (I/G bit 0) addresses one interface; multicast (bit 1) addresses a group. For a normal interface you want unicast, which is the default.

Is anything sent to a server?

No. Generation uses your browser's random number generator and runs entirely client-side.

🎓 Pro Tips

  • Tip 1: Keep 'locally administered' on for invented addresses — it's the standards-correct way to avoid colliding with a real manufacturer's OUI.
  • Tip 2: For reproducible lab setups, pin a private OUI prefix so all your test devices share a recognizable vendor block.
  • Tip 3: A MAC is unique on a LAN, not secret — don't treat a generated MAC as a security token.