Random MAC Address Generator
Generate random MAC addresses with the right I/G and U/L bits, in colon, hyphen or Cisco dot format.
First address, decoded
- Address
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- OUI (first 3 bytes)
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- First octet in binary
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- I/G bit (bit 0)
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- U/L bit (bit 1)
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- IPv6 link-local (modified EUI-64)
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Addresses are drawn from crypto.getRandomValues() inside your browser.
Nothing is generated on a server, nothing is transmitted and nothing is stored.
How it works
A MAC address is 48 bits — six bytes, usually written as twelve hex digits. The two
lowest bits of the first byte carry meaning: bit 0 is the I/G bit
(0 = unicast, 1 = multicast) and bit 1 is the U/L bit
(0 = universally administered, i.e. built from an IEEE-assigned OUI,
1 = locally administered). “Locally administered, unicast” therefore forces the
first byte to xxxxxx10 — that is the range reserved for made-up addresses,
so it can never collide with a real vendor’s allocation. The other modes let you clear
the U/L bit, set the I/G bit, or pin the first three bytes to a real vendor prefix such
as VMware’s 00:50:56 or VirtualBox’s 08:00:27.
The decoder below the output explains the first generated address bit by bit and derives
its IPv6 link-local address using modified EUI-64: flip the U/L bit of the first byte,
insert FF:FE in the middle, and prefix fe80:: — so
00:1A:2B:3C:4D:5E becomes fe80::21a:2bff:fe3c:4d5e. The vendor
list is a small curated set of prefixes people actually search for, not the full IEEE
registry. Every byte is produced locally by the Web Crypto random generator: no sign-up,
no ads, no network requests, and the page keeps working offline once loaded.
Frequently asked questions
How do I generate a random MAC address?
Pick how many you need and press Generate. By default the tool sets the first octet to the pattern xxxxxx10 — bit 0 clear (unicast) and bit 1 set (locally administered) — so the address is valid for a network interface and can never collide with an IEEE-registered vendor block. The remaining 46 bits come from crypto.getRandomValues() in your browser.
What is a locally administered MAC address?
Bit 1 of the first byte is the U/L bit. When it is 0 the address is universally administered, meaning the first three bytes are an OUI the IEEE assigned to a manufacturer. When it is 1 the address is locally administered — reserved for addresses you assign yourself, which is exactly what you want when spoofing or testing. Bit 0 is the I/G bit: 0 for unicast, 1 for multicast.
Can I generate a MAC address for a specific vendor like VMware or VirtualBox?
Yes. Choose "Fixed vendor prefix (OUI)" and pick a prefix such as 00:50:56 (VMware), 08:00:27 (VirtualBox), 52:54:00 (QEMU/KVM) or 00:15:5D (Hyper-V), or type any 3-byte OUI yourself. The last three bytes stay random. The vendor list is a small curated selection, not the full IEEE registry.