What do the first three bytes mean?

They encode the OUI (Organizationally Unique Identifier), the vendor prefix assigned to manufacturers. Random OUIs may not map to a real vendor; locally administered addresses are clearly flagged by the second-least-significant bit of the first byte.

Can I use these addresses for anything?

They are handy for testing, mock data and network simulators. Real network devices on managed networks can be restricted by MAC filtering — these random addresses are only for test environments.

What does "locally administered" change?

It sets the second-least-significant bit of the first byte, marking the address as locally assigned rather than vendor-assigned. This avoids pretending the address belongs to a real manufacturer, which is useful in virtualized and test networks.

Can I choose the vendor prefix (OUI)?

Yes. Enter the first three bytes in the fixed-prefix field and the last three bytes remain random. The prefix must be exactly three hex bytes, for example 00:1A:2B.

Why do generated addresses start with 00:00:00?

When the prefix field is empty, the first three bytes are left as zeros and only the last three are random. Enter a vendor prefix such as 00:1A:2B when you need realistic test data with a specific OUI.

MAC Address Generator

Generate random MAC addresses in several formats.

Frequently asked questions

What do the first three bytes mean?: They encode the OUI (Organizationally Unique Identifier), the vendor prefix assigned to manufacturers. Random OUIs may not map to a real vendor; locally administered addresses are clearly flagged by the second-least-significant bit of the first byte.
Can I use these addresses for anything?: They are handy for testing, mock data and network simulators. Real network devices on managed networks can be restricted by MAC filtering — these random addresses are only for test environments.
What does "locally administered" change?: It sets the second-least-significant bit of the first byte, marking the address as locally assigned rather than vendor-assigned. This avoids pretending the address belongs to a real manufacturer, which is useful in virtualized and test networks.
Can I choose the vendor prefix (OUI)?: Yes. Enter the first three bytes in the fixed-prefix field and the last three bytes remain random. The prefix must be exactly three hex bytes, for example 00:1A:2B.
Why do generated addresses start with 00:00:00?: When the prefix field is empty, the first three bytes are left as zeros and only the last three are random. Enter a vendor prefix such as 00:1A:2B when you need realistic test data with a specific OUI.

About this tool

A MAC address is a 48-bit hardware identifier written as six hexadecimal bytes. This generator creates random addresses for test data, network simulators and lab environments, with control over the separator, letter case, a fixed OUI prefix and the locally-administered bit.

How to use it

Set how many addresses to generate.
Choose colons, hyphens or no separator, and upper or lower case.
Optionally fix the first three bytes (the OUI) with a prefix such as 00:1A:2B.
Copy the addresses from the main result or the full list.

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