MAC Address Lookup

Paste a MAC address in any format — colons, hyphens, Cisco dotted triples or bare hex — and get the organisation that registered it, along with every alternate representation and the IPv6 interface identifier derived from it.

The whole IEEE registry is bundled with this page: MA-L, MA-M, MA-S and the legacy IAB blocks, around 58,000 assignments. That is a larger download than any other tool here, and it is deliberate. Every other MAC lookup on the web posts the address to a server, and the addresses people look up come out of Wi-Fi scans, DHCP tables and security logs — records about specific devices in specific places. Here the search runs in your browser and the address is never transmitted. The smaller registries are included for a second reason: a 28-bit or 36-bit assignment sits inside a block the IEEE holds itself, so a lookup that only knew the 24-bit registry would confidently answer "IEEE Registration Authority" for an address that belongs to a named company.

Just as important is knowing when there is no answer to find. The second bit of the first octet marks an address as locally administered — assigned by software, never registered — and that is what a modern phone or laptop uses when scanning for Wi-Fi, specifically so that networks cannot follow it between visits. A lookup tool that reports "vendor not found" for one of those is hiding the actual answer, which is that no vendor exists and never will. The low bit marks a multicast group rather than a device. Both bits are shown and explained on every result, and the well-known addresses — broadcast, IPv4 and IPv6 multicast, spanning tree — are named outright.

The EUI-64 and link-local address are derived too, including the step that is nearly always done wrong by hand: forming an IPv6 interface identifier inserts ff:fe in the middle and inverts the universal/local bit, so 00:14:51 becomes 02:14:51 (RFC 4291).