What does the prefix option do?

The first three bytes (OUI) encode the manufacturer. Setting a prefix makes the generated addresses look like they belong to a given vendor — handy when your system parses or routes on OUI.

Are these safe to use in documentation?

Yes for examples and tests. Do not reuse them to spoof devices on networks you do not own — MAC filtering and logging exist for a reason.

Why upper versus lower case?

IEEE records use colon-separated lower case, while many Windows tools print upper case. The bytes are identical; pick the convention your target system expects to avoid string-comparison bugs.

Why does my prefix of A come back as 0A?

Because prefix bytes are left-padded to two hex digits, not right-padded: a lone “A” is read as the byte 0x0A. If you meant the address to start with A0, write the prefix as “A0”. The same rule applies to any odd-length prefix, which is why pasting a half-written OUI silently shifts every nibble.

Does the generator keep the address unicast?

No. Only the bytes you supply as a prefix are controlled; the rest are uniform random over 0-255, which means the least-significant bit of the first octet (multicast) and the second-least-significant bit (locally administered) are decided by chance. Pin the first octet if either property matters to you.

MAC address generator — Guide

Enter the quantity and prefix. MAC addresses will be generated in your chosen case (uppercase or lowercase)

What it is and when to use it

Generate random MAC addresses, optionally anchored to a prefix you supply. Type an OUI or the first few octets and the remaining bytes are filled with random values, then joined with your chosen separator and cased the way you want — handy for test fixtures, documentation examples, mock device inventories and UI state that needs a plausible-looking hardware address without reusing a real one. Prefix bytes are used exactly as written and left-padded to two hex digits, so “A” becomes 0A rather than A0.

Generates MAC addresses in bulk for testing network gear or fabricating test data.

How to use it

Enter how many you need
Add a prefix if required
Click generate and copy

A worked example

Fill in quantity 10

Copy this into the tool, or open MAC address generator

Things that trip people up

The first octet is random unless you pin it, so the generated address may set the multicast or globally-unique bits — it is not forced to be locally-administered unicast.
A prefix longer than six groups yields more than six octets; the tool does not trim to six.
These are random values, not allocated addresses: they are safe as fixtures, but they are not reserved by any standard.

Questions people ask

What does the prefix option do?: The first three bytes (OUI) encode the manufacturer. Setting a prefix makes the generated addresses look like they belong to a given vendor — handy when your system parses or routes on OUI.
Are these safe to use in documentation?: Yes for examples and tests. Do not reuse them to spoof devices on networks you do not own — MAC filtering and logging exist for a reason.
Why upper versus lower case?: IEEE records use colon-separated lower case, while many Windows tools print upper case. The bytes are identical; pick the convention your target system expects to avoid string-comparison bugs.
Why does my prefix of A come back as 0A?: Because prefix bytes are left-padded to two hex digits, not right-padded: a lone “A” is read as the byte 0x0A. If you meant the address to start with A0, write the prefix as “A0”. The same rule applies to any odd-length prefix, which is why pasting a half-written OUI silently shifts every nibble.
Does the generator keep the address unicast?: No. Only the bytes you supply as a prefix are controlled; the rest are uniform random over 0-255, which means the least-significant bit of the first octet (multicast) and the second-least-significant bit (locally administered) are decided by chance. Pin the first octet if either property matters to you.

Next steps

Open the MAC address generator tool

Spotted something wrong on this page? Tell us via Contact Us