Free MAC address lookup

A network interface doesn't invent its address — the first half of it is bought. A manufacturer pays IEEE for a block, and every card they ship gets an address inside that block. So A4:83:E7 at the front of A4:83:E7:2B:0C:1F is registered to Apple, and the six digits after it are Apple's own counter. Match the prefix, read the company. That's the whole mechanism, and it's why a lookup can name the maker of a device you've never seen.

We build asset-tracking software, so treat the pitch above with the skepticism it deserves. The tool itself has nothing to sell you: it loads a registry file and does string matching in your tab.

Why other lookups say "IEEE Registration Authority"

Ask around and you'll hear this reported as a bug. It isn't. IEEE sells three sizes of block, and most tools only load the biggest one.

MA-L is the classic 24-bit OUI — three octets, about 40,000 of them issued, and what everyone means by "the OUI database". Fine for Apple, Cisco, Samsung. But a company that needs a few thousand addresses rather than sixteen million buys an MA-M (28-bit) or MA-S (36-bit) block, and those live inside an MA-L block that IEEE registers to itself. Look up 8C:1F:64:AF:A1:23 against MA-L alone and you get "IEEE Registration Authority", which is technically correct and completely useless. Check the 36-bit prefix first and you get DATA ELECTRONIC DEVICES, INC.

This tool loads all three — 53,784 records — and always matches the longest block first.

The address tells you who made the chip, not what the box is

Worth being blunt about, because it trips up asset audits constantly: a MAC identifies whoever built the network interface. A Dell laptop with an Intel Wi-Fi card reports Intel. A whitebox NAS reports whichever Realtek part is soldered to the board. Hyper-V guests report Microsoft, VMware guests report 00:50:56, and neither says anything about the workload inside.

For network troubleshooting that's usually enough — you're trying to work out whether the unknown thing on VLAN 30 is a printer or somebody's TV. For an equipment register it isn't, and no lookup will fix that. Serial numbers and asset tags survive a NIC swap; MAC addresses don't.

Randomized addresses, and why half your Wi-Fi table is now junk

Since iOS 14 and Android 10, phones present a different, made-up MAC to every network they join. These are marked in the address itself: if the second hex digit is 2, 6, A or E, the U/L bit is set and the address is locally administered. No vendor owns it. No lookup can name it, here or anywhere else, and any site that returns a manufacturer for one is guessing.

The tool flags them rather than shrugging. Same for multicast and broadcast addresses, which turn up in pasted arp -a output and aren't device identifiers at all.

If you're building a device inventory off Wi-Fi MACs, this is the part that quietly breaks it. Wired ports still behave.

Pasting a real list

Bulk mode takes up to 1,000 addresses and doesn't care about column order. Feed it arp -a output, a DHCP lease export, a CSV from your switch — anything on the line that isn't the address becomes the label, so the CSV that comes back still says which row was the reception printer. Colons, hyphens, Cisco dotted notation and bare hex all parse, mixed together in the same paste if that's what you have. Duplicates get marked instead of dropped, because merged ARP dumps are full of them and the count matters.

Nothing downloads until you type. Then the page pulls only the slice of the registry your addresses need — one file per leading octet, about 6 KB each — rather than the whole 1.7 MB list, and falls back to the full file only when a paste is spread across enough octets that fetching them one by one stops paying off. Every match happens locally either way. If you want the raw list yourself, IEEE publishes it at standards-oui.ieee.org.

Working out which subnet those devices sit on instead? The subnet calculator does the mask arithmetic and checks a pasted IP plan for overlaps. Generating labels rather than reading addresses? The bulk barcode generator turns a list or CSV into a printable sheet, and the barcode scanner reads tags back with a camera.