MAC Address Info
Parse MAC addresses in any format. Vendor lookup, unicast/multicast and universal/local detection, EUI-64 conversion, and IPv6 interface identifier derivation.
Formats
- Colons (RFC 4949)
00:1B:21:11:22:33- Hyphens (IEEE 802)
00-1B-21-11-22-33- Cisco dots
001b.2111.2233- No separator
001b21112233
Address type
- Unicast / Multicast
- Unicast
- Universal / Local
- Universal (factory-assigned)
Vendor (OUI lookup)
- OUI (first 24 bits)
- 00:1B:21
- Registered vendor
- Intel Corporate
Embedded OUI list covers 472+ common vendors. For exhaustive lookup, use the IEEE registry.
EUI-64 (IPv6 interface identifier)
- Full EUI-64
02:1B:21:FF:FE:11:22:33- IPv6 IID (last 64 bits)
::021b:21ff:fe11:2233
EUI-64 derives an IPv6 interface ID from the MAC by inserting FF:FE in the middle and flipping the universal/local bit. Modern stacks prefer RFC 4941 temporary addresses or RFC 7217 stable privacy addresses to avoid tracking across networks.
About this tool
A MAC address is a 48-bit identifier assigned to a network interface (Ethernet, WiFi, Bluetooth). The first 24 bits identify the vendor via an OUI (Organizationally Unique Identifier) assigned by the IEEE, and the remaining 24 bits are assigned by the vendor to uniquely identify the device within their allocation. Two flag bits in the first byte carry structural meaning: bit 0 is Unicast/Multicast (0 = unicast, 1 = multicast), and bit 1 is Universal/Local (0 = factory-assigned, 1 = locally administered).
Paste a MAC in any common format — colons, hyphens, Cisco four-digit
dots, or no separators — and the tool normalizes it, looks up the
vendor, flags the address type, and shows conversions across formats.
If the first byte is odd, the address is multicast; the tool calls
out the well-known multicast prefixes 01:00:5E (IPv4
multicast), 33:33 (IPv6 multicast), and
01:80:C2 (bridge/spanning-tree), as well as the
broadcast FF:FF:FF:FF:FF:FF.
Burned-in vs locally administered: a factory-assigned MAC has the universal/local bit clear, meaning it was issued from an IEEE-assigned OUI and should be unique globally. A locally administered MAC has the bit set, meaning the address was chosen by the OS, VM manager, or user — typical cases include Docker containers, virtualization hypervisors picking random MACs for guest NICs, and phones randomizing MACs per-network to prevent tracking. The tool flags these explicitly so you know not to look up the vendor.
EUI-64 conversion derives a 64-bit IPv6 interface
identifier from a 48-bit MAC: insert FF:FE in the middle
and flip the universal/local bit. The result combines with a /64
prefix from your router advertisement to form a full IPv6 address
(SLAAC). Modern OSes often skip EUI-64 in favor of random or
per-network-stable identifiers (RFC 4941, RFC 7217), because
broadcasting your MAC across the public Internet lets websites
fingerprint your device.
Vendor lookup uses an embedded database of common OUIs covering major device manufacturers — Apple, Samsung, Intel, Cisco, Dell, HP, Raspberry Pi, Amazon, Google, Microsoft, VMware, Roku, and hundreds of others. For a full IEEE registry lookup, the Wireshark OUI tool is the best online source. The embedded list keeps the tool fast and works offline.
Frequently asked questions
Why are there so many MAC address formats?
Different platforms settled on different separators. Colons are standard in Unix and RFC 4949 (aa:bb:cc:dd:ee:ff). Hyphens are used in Windows and older IEEE 802 documentation (aa-bb-cc-dd-ee-ff). Cisco equipment uses four-digit dot groups (aabb.ccdd.eeff). The bare hex form (aabbccddeeff) is common in config files. They all represent the same 48 bits — the tool converts between them.
Can MAC addresses collide?
In principle yes — 48 bits gives 281 trillion addresses, and the first 24 bits are vendor-assigned (OUI), leaving each vendor 16 million addresses. Vendors are responsible for uniqueness within their OUIs. Collisions across vendors are astronomically rare in practice but theoretically possible, especially with counterfeit hardware or misconfigured virtualization.
Why does my phone show a different MAC on different networks?
Modern iOS, Android, Windows, and Linux all support MAC randomization to prevent cross-network tracking. When you join a WiFi network, the OS picks a random locally administered address for that network. The universal/local bit (bit 1 of the first byte) is set to 1 to flag that the MAC is not the factory-assigned one. The tool flags locally administered addresses explicitly.
Why are MAC-derived IPv6 addresses a privacy concern?
EUI-64 (deriving the IPv6 interface identifier from the MAC) means every packet your device sends contains your MAC in the source address. A website could correlate your visits across any network you join. RFC 4941 (temporary addresses) and RFC 7217 (stable but per-network) fix this. Most modern OSes default to one of these; EUI-64 is increasingly rare.
How do I find my own MAC address?
macOS/Linux: ifconfig or ip link show. Windows: ipconfig /all or Get-NetAdapter in PowerShell. iOS: Settings → General → About. Android: Settings → About phone → Status. Modern phones may show "randomized" MACs — look for the option to use the factory-assigned hardware MAC, or just join a network and check it from the router.