OUI Resolve is a free utility that resolves a MAC address — or just its 24-bit OUI prefix — to the organization that registered it, and decodes the structural bits of the address that actually matter when you're troubleshooting a network.
Vendor assignments are factual records published by the IEEE Registration Authority, which administers the MA-L, MA-M, and MA-S blocks. We build a local copy from that authoritative source so lookups are fast and reliable. When an entry isn't in our local copy, the tool falls back to public vendor-lookup APIs, then reports which source answered. This layered approach means a result still comes back even if one source is incomplete or temporarily offline.
Network engineers, system administrators, NOC and SOC analysts, security researchers, students studying for networking certifications, and anyone trying to figure out what that unknown device on their network actually is.
OUI Resolve is built and maintained by Frederick Premuto, a cybersecurity and network operations professional with 14+ years of military and private-sector experience spanning enterprise network security, PKI and identity management, Zero Trust architecture, and vulnerability management — the same day-to-day work this toolkit is built to support. The tool exists because the everyday job of identifying a device from its MAC deserved a resolver that's accurate, fast, transparent about its sources, and pleasant to use.
We rebuild from the IEEE registry regularly to stay current, and we're transparent that no vendor database is ever perfectly complete. If you spot something wrong, tell us on the Contact page and we'll correct it. How we handle data is described in our Privacy Policy.