Random MAC Address Generator

Generate valid random MAC addresses in any common notation — colon (01:23:45:67:89:ab), hyphen, Cisco dotted (0123.4567.89ab), or no separator — in upper or lowercase. Useful for test fixtures, network labs, virtual machines, and documentation.

How it works

A MAC address is 48 bits, shown as six bytes. The tool draws six random bytes from the browser’s secure random generator, then adjusts the first octet’s two low-order bits so the result is a proper, safe address: it sets the locally-administered bit (so the address is marked as locally assigned, not allocated to a hardware vendor via an OUI) and clears the multicast bit (so it is unicast). This guarantees the address is a valid, locally-administered unicast MAC that cannot collide with real vendor-assigned hardware.

The remaining bits are fully random. The bytes are then formatted with your chosen separator and letter case.

Understanding the two control bits

The first octet of a MAC address encodes two status flags in its least-significant bits:

For test and lab use you want unicast + locally administered: unicast because you are addressing a single interface, and locally administered because it signals the address is not assigned by a hardware vendor. Setting the locally-administered bit (bit 1 of byte 0) while clearing the multicast bit (bit 0 of byte 0) achieves this.

The first octet a2 in hexadecimal is 1010 0010 in binary. Bit 1 (the locally-administered bit) is 1 and bit 0 (the multicast bit) is 0 — exactly what a valid random unicast, locally-administered MAC requires.

Common use cases

Virtual machines. Hypervisors including VMware, VirtualBox, and QEMU assign locally-administered MACs to virtual network interfaces. Generating one here lets you pre-configure VM network settings before the VM is started, or assign a consistent MAC so DHCP reservations work reliably.

Network testing and automation. Test scripts that simulate multiple network devices need MAC addresses for each simulated interface. A batch of random locally-administered MACs avoids collisions with any physical hardware on the same segment.

Documentation and examples. Technical writing, diagrams, and tutorials need realistic-looking addresses that are obviously not real hardware. Locally-administered addresses are the correct choice — they are structurally valid but unambiguously not from any real manufacturer.

MAC address spoofing for privacy. Many operating systems allow temporary MAC address randomisation for Wi-Fi scanning to prevent tracking. The locally-administered bit is used as the signal that the address is ephemeral. This calculator generates addresses in the same format.

Format comparison

Generation happens entirely in your browser; nothing is sent anywhere.