Generate random MAC addresses with colon, hyphen, dot or bare formatting. The locally administered bit is set by default so generated addresses cannot collide with a manufacturer-assigned range, and the multicast bit is exposed as its own option.
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Where a MAC address sits
Network addressing works in layers. An IP address identifies a host across the internet and can change as a device moves between networks. A MAC address identifies an interface on the local segment and is used to deliver frames to the right piece of hardware once traffic has arrived on that network. When your computer sends a packet to a machine on the same network, it resolves the target’s IP address to a MAC address first, then addresses the frame to it.
The address is 48 bits, conventionally written as twelve hexadecimal digits. The first three bytes traditionally identify the manufacturer; the remaining three are assigned by that manufacturer to individual interfaces.
Two bits that change the meaning
The first byte carries two flags in its lowest bits, and they are the reason a MAC generator needs more than a random-number call.
The least-significant bit is the unicast/multicast flag. Clear means the frame is destined for a single interface; set means it addresses a group. An address with this bit set is not a valid device identifier, so it should be off unless you are specifically generating multicast addresses.
The next bit up is the universal/local flag. Clear means the address came from a manufacturer’s registered range. Set means it was assigned locally and carries no vendor meaning. This is the important one for generated addresses: with the local bit set, the value provably cannot collide with real hardware, because manufacturers never assign addresses with that bit on.
Generating twelve random hex digits without touching these bits produces an address that will usually claim to be manufacturer-assigned, and may fall inside a range genuinely registered to a company. Setting the local bit is what makes a generated address correct rather than merely well-formed.
Vendor identification and its limits
Because the first three bytes are registered, a manufacturer-assigned MAC address can often be mapped to a vendor. Network administrators use this to identify unknown devices, and it is why an inventory tool can report that a machine on the network is a particular brand of printer.
It identifies the manufacturer of the interface, not the device’s owner or its purpose. And it only works for universally administered addresses — a locally administered one, including every address this tool generates by default, has no vendor to look up.
Randomisation and privacy
A MAC address was historically a fixed, globally unique identifier that a device broadcast constantly while looking for networks. That made it an excellent tracking beacon: a shop with wireless access points could recognise the same phone returning day after day, with no consent and no way to opt out.
Modern mobile operating systems randomise the address used when scanning, and often present a different address to each network they join. The randomised addresses are locally administered — the same bit this tool sets — precisely so they cannot be confused with real hardware identifiers. If you are building anything that reasons about MAC addresses, assume they are neither stable nor unique per device.
Notation
Colons, hyphens and Cisco’s four-digit dotted groups all encode the same 48 bits. Case is insignificant, as it is anywhere in hexadecimal. Software that compares addresses should normalise the separators and case first, since two spellings of the same address are the same address — a comparison that fails because one side used hyphens is a bug that appears only when a value crosses a system boundary.
Privacy
Addresses are generated in your browser. Your device’s real MAC address is not accessible to a web page and is never read. Nothing generated here is transmitted, stored or logged.
How to use the Random MAC Address Generator
- Choose a separator style to match the system you are targeting.
- Leave "locally administered" on so the address cannot collide with real hardware.
- Set how many addresses you need.
- Generate, then copy or export as CSV.
Frequently asked questions
What is a MAC address?
A 48-bit identifier assigned to a network interface, written as twelve hexadecimal digits. It operates at the link layer, identifying a device on the local network segment — unlike an IP address, which identifies it on the wider network.
What does "locally administered" mean?
The second-least-significant bit of the first byte marks whether an address was assigned by a manufacturer or set locally. With that bit on, the address is declared local and cannot collide with any manufacturer-assigned value. It is on by default here, because that is what makes a generated address safe to use in testing.
What is an OUI?
The first three bytes of a manufacturer-assigned address form an Organisationally Unique Identifier, registered to a specific company. It is why a MAC address can often be traced to a hardware vendor. Locally administered addresses deliberately have no meaningful OUI.
What is the multicast bit?
The least-significant bit of the first byte. When clear, the frame is for one recipient; when set, it is for a group. An address with that bit set is not valid as a device identifier, which is why the option is off by default and separate from the local bit.
Why are there so many separator styles?
Different systems adopted different conventions. Colons are common on Unix-like systems, hyphens on Windows and in many printed labels, and the four-digit dotted style in Cisco equipment. They all describe the same 48 bits, and matching the target format saves a conversion step.
Can I use a generated MAC to spoof a device?
These are for testing, documentation and fixtures. Changing a device's MAC address is a legitimate technique in some contexts and prohibited in others, particularly on networks that authenticate by hardware address. Whether it is acceptable depends on the network you are on and whose it is.
Does a MAC address identify me?
It identifies a network interface, and historically it was a stable identifier that could be used to track a device across networks. Modern phones and laptops randomise the address they present when scanning for or joining networks, specifically to prevent that tracking. Your own MAC address is never read by this tool.
