What is a locally-administered MAC address?

It is a MAC whose second-least-significant bit of the first octet is set, marking it as assigned locally rather than by a hardware vendor. Random MACs should set this bit so they cannot collide with real OUI-assigned addresses.

Are these addresses tied to real devices?

No. They are random sample values. With the default option enabled they are valid unicast, locally-administered addresses suitable for test fixtures and labs.

Is anything sent over the network?

No. Addresses are generated entirely in your browser with a secure random generator and never transmitted.

Random MAC Address Generator

Valid random MAC addresses in any format — colon, hyphen, Cisco.

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.

By default the locally-administered unicast bit is set, so every address is a legitimate MAC that can never collide with a vendor-assigned hardware address. Generation happens in your browser with a secure random generator; nothing is sent anywhere.