MAC Address Lookup is an online reference service that helps users identify the organization registered to a network device’s MAC address or address prefix. Built from public IEEE Registration Authority data, its database covers 58,487 assignments associated with 34,073 organizations and is re-imported daily. Users can search by entering a full address or prefix, with or without common separators, and see results as they type.

The site also provides bulk lookup for up to 2,000 addresses, with CSV export, plus a generator for random MAC addresses and an inspector for converting formats and interpreting address bits. A vendor discovery tool lets users search registry organizations using filters and sorting. Developers can access the same data through a free API offering JSON, XML, CSV, or pipe-delimited output, with no key or sign-up required.

The service resolves lookups in the browser using published registry files, so full MAC addresses are not sent to a server. Additional resources include registry statistics, an FAQ, and a current Cisco vendor file for network management systems