MAC Address Vendor (OUI) Lookup & Formatter
Look up the vendor (OUI) for any MAC address against a bundled IEEE registry (200+ vendors, MA-L/MA-M/MA-S/IAB longest-prefix matching), reformat between colon, hyphen, Cisco dot, and bare hex notations, decode U/L (locally-administered) and I/G (multicast) bits, reverse-search vendor → prefixes, generate random vendor-correct MACs, batch lookup, and CSV export. 100% client-side, offline, no network.
About MAC Address Vendor (OUI) Lookup & Formatter
Look up the vendor (OUI) for any MAC address against a bundled IEEE registry (200+ vendors, MA-L/MA-M/MA-S/IAB longest-prefix matching), reformat between colon, hyphen, Cisco dot, and bare hex notations, decode U/L (locally-administered) and I/G (multicast) bits, reverse-search vendor → prefixes, generate random vendor-correct MACs, batch lookup, and CSV export. 100% client-side, offline, no network. Everything runs locally in your browser — your data never leaves your device.
How to use
- Enter your input in the tool above.
- Adjust any options to your preference.
- Use the Copy or Download buttons to save the result.
- Everything happens locally — your data never leaves your browser.
FAQ
How does the MAC vendor lookup work?
We bundle a curated IEEE OUI registry of 200+ common vendor prefixes. When you enter a MAC, the tool extracts the prefix and walks the registry with longest-prefix matching — so the 28-bit MA-M and 36-bit MA-S/IAB blocks (e.g. 70-B3-D5-1-x-x for MA-M, 5C-1D-D9-6-x-x-x for IAB) resolve correctly, not just the flat 24-bit OUI. The DB is clearly dated in-app, so very recent registrations may not resolve until the bundle is refreshed.
What MAC formats are supported for input and output?
Input accepts any common separator — colon (00:1A:2B:3C:4D:5E), hyphen (00-1A-2B-3C-4D-5E), Cisco dot (001A.2B3C.4D5E), bare hex (001A2B3C4D5E), and EUI-64 forms (00:1A:2B:FF:FE:3C:4D:5E with the FFFE insert, or 00:1A:2B:3C:4D:5E:6F:7E raw). Output re-formats into colon, hyphen, Cisco dot, or bare hex, in upper or lower case, and all conversions are reversible.
What do the U/L and I/G bits mean?
The first octet of a MAC has two flag bits. Bit 1 (second-least-significant) is the U/L bit: 0 = universally administered (UAA, assigned by IEEE), 1 = locally administered (LAA, set by the device owner — common in VMs, Bluetooth randomization, and privacy MACs on phones). Bit 0 (least-significant) is the I/G bit: 0 = unicast, 1 = multicast (e.g. IPv4 broadcast FF:FF:FF:FF:FF:FF, IPv6 multicast 33:33:...). The tool decodes both bits and flags LAA / multicast MACs.
Can I generate vendor-correct random MACs for testing?
Yes. The random generator can produce (1) fully random MACs, (2) vendor-correct MACs that start with a chosen vendor's OUI prefix, (3) locally-administered (LAA) MACs with the U/L bit set — useful for VMs and privacy testing, and (4) multicast MACs with the I/G bit set. Bulk generate up to 1,000 per click with seeded PRNG for reproducible fixtures.
What extra features does this tool have versus other OUI lookup sites?
(1) Bundled IEEE OUI DB with 200+ common vendors — fully offline. (2) MA-L/MA-M/MA-S/IAB longest-prefix matching (28/36-bit). (3) Five output formats (colon/hyphen/Cisco-dot/bare/EUI-64) with case toggle. (4) U/L and I/G bit decoding. (5) Reverse search vendor → matching prefixes. (6) Batch lookup of many MACs. (7) Random vendor-correct MAC generator (LAA/UAA/multicast modes). (8) CSV + JSON export. (9) EUI-48 ↔ EUI-64 conversion. (10) Broadcast/multicast detection. (11) Bulk validation summary. (12) Deterministic seeded PRNG. (13) localStorage history (max 20, no MACs stored). (14) Shareable URL. 100% client-side — your MACs never leave the browser.
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