MAC Address Lookup
Paste a MAC in any format and read back the OUI vendor, the cast and admin bits, the VM prefix and every spelling.
This MAC address lookup takes the first half of any MAC and tells you who built the network card. Paste a MAC with colons, dashes, dots, or no separators at all, and the tool pulls the OUI, the first 24 bits IEEE assigns to a manufacturer, and matches it against a curated set of common hardware and virtualization vendors. It also decodes the bits that actually matter on the wire: unicast versus multicast, globally unique versus locally administered, and whether the address is one of those randomized privacy MACs your phone hands out per network. Recognized virtual machine prefixes for VMware, Hyper-V, VirtualBox, Xen, QEMU and Docker get flagged on sight. You get every canonical spelling for copy and paste, plus an honest note when a prefix sits outside the common set. It all runs in your browser and nothing you paste ever leaves the page.
100% in your browser. Nothing you type ever leaves this page.
Local MAC and OUI utility
Every network card is born with a name tag stitched into the first half of its MAC address. That chunk is the OUI, and it tells you who built the thing. I keep reaching for this when a rogue device shows up in the DHCP table and I want a hint before I go walking the patch panel. Paste a MAC in any format you like (colons, dashes, dots, or no separators at all) and you get the vendor guess plus the bits that actually matter: is it unicast or multicast, real burned-in hardware or a randomized privacy address, and is it one of those virtual machine prefixes worth recognizing on sight.
Everything runs in your browser. Nothing you paste ever leaves the page. Heads-up: this matches against a curated list of common vendors, not the full IEEE registry of 30,000-plus assignments. A miss here does not mean the OUI is unassigned, it just means it is not in our common set.
What an OUI is, and how a MAC splits in two
A MAC address lookup starts with one idea: a MAC address is 48 bits, six bytes, and it falls into two halves that do very different jobs. The first three bytes are the OUI, the Organizationally Unique Identifier. IEEE sells those to manufacturers, so the OUI is basically the vendor's fingerprint. The last three bytes are the device portion, picked by that vendor to keep each unit unique. So a MAC like 00:1A:2B:3C:4D:5E reads as "OUI 00:1A:2B, then device 3C:4D:5E". Knowing where the cut falls is the whole trick. You take the first 24 bits, look them up, and the vendor pops out.
One wrinkle worth knowing. IEEE also sells smaller blocks now, the MA-M (28-bit) and MA-S (36-bit) registries, where several companies share a single 24-bit prefix and split the rest. Our tool still matches on the plain 24-bit prefix, which is what almost everyone means by "OUI lookup", but on those shared blocks the 24-bit answer can be the block holder rather than the exact sub-licensee. For the vast majority of gear, the 24-bit match is the right answer.
The U/L bit, and why your phone lies about its MAC
Here is the part that trips people up. Not every MAC is a real, factory-assigned address. The second-lowest bit of the very first byte is the U/L bit, universal versus local. When it is 0, the address is globally unique, burned in at the factory, and the OUI is meaningful. When it is 1, the address is locally administered, made up on the spot, and the OUI means nothing. There is no vendor behind it.
This used to be rare. Now it is everywhere, because modern phones randomize their MAC per network for privacy. iPhones and Android both do it by default. The randomized address always has the U/L bit set to 1, which is your tell. So if you look up a phone's Wi-Fi MAC and get a nonsense vendor or no match at all, that is not a bug. The phone is deliberately hiding. Any honest lookup tool has to flag that bit, and ours does, loudly, because guessing a vendor for a randomized MAC is just making things up.
Virtualization prefixes worth memorizing
If you run any virtual infrastructure, a handful of OUI prefixes are worth knowing cold. VMware hands out two famous ones: 00:50:56 for manually or vCenter-assigned NICs, and 00:0C:29 for older auto-generated ones. VirtualBox uses 08:00:27. Microsoft Hyper-V uses 00:15:5D. Xen shows up as 00:16:3E. QEMU and KVM default to 52:54:00, which also happens to have the locally-administered bit set. Docker containers usually start 02:42, again locally administered. Spot one of these in a capture and you instantly know you are looking at a guest, not bare metal. That alone has saved me a fair bit of "why can't I find this server" confusion.
When vendor lookup helps, and when it quietly lies
The honest pitch: OUI lookup is a hint, not proof. It is genuinely useful for inventory ("what are all these unknown devices on the guest VLAN?"), for spotting a vendor that should not be there, and for sanity-checking a capture. Where it lies: randomized phone MACs (no real vendor), white-label hardware where the OUI belongs to the chipset maker rather than the brand on the box, and spoofed addresses (a MAC is trivially easy to change). Treat the vendor as a lead to chase, never as identity. And for anything outside our common-vendor set, go to the source: the official IEEE registry has every assignment.
Sources and further reading
- IEEE Registration Authority, official OUI and company ID lookup
- IEEE OUI assignment file (oui.txt), the full registry
- Wireshark OUI lookup tool
Frequently asked questions
What is an OUI in a MAC address?
It is the Organizationally Unique Identifier, the first 24 bits (three bytes) of a MAC. IEEE assigns these blocks to manufacturers, so the OUI identifies who made the network interface. The remaining 24 bits are chosen by that vendor to keep each device unique.
Why does my phone's MAC show no vendor?
Because it is almost certainly a randomized, locally administered address. Modern iPhones and Android phones invent a fresh MAC per Wi-Fi network for privacy. Those addresses have the U/L bit set to 1 and carry no real OUI, so there is no genuine vendor to find. The tool flags that for you.
Is this the full IEEE database?
No, and I would rather be upfront about it. This is a curated set of roughly 250 common and high-value prefixes: the big hardware brands plus the virtualization vendors sysadmins actually run into. The real IEEE registry holds well over 30,000 assignments. If your prefix is not here, check the official IEEE OUI lookup linked in the sources.
Can I trust a MAC address to identify a device?
Only loosely. A MAC is easy to change in software, randomized by default on phones, and on cheap gear the OUI often points at the chipset vendor rather than the brand. Use it as a strong hint during troubleshooting or inventory, but never as proof of identity for anything that matters.