What kind of MAC addresses does this generate?

Six-byte, 48-bit EUI-style address fixtures with the locally administered bit set and the multicast bit clear. They are synthetic local unicast addresses, not hardware identities or IEEE-assigned vendor addresses. The tool does not change device or network settings.

What do the U/L and I/G bits mean?

In the first octet, bit 1 is the universal/local bit: this generator sets it to 1 for local administration. Bit 0 is the individual/group bit: it is cleared to 0 for unicast. Together, the first octet always satisfies (byte & 3) == 2. The other bits are random unless fixed by your prefix.

Which fixed prefixes are accepted?

Enter one to three complete hex octets, with no separator or a consistent colon or hyphen separator. Examples are 02, 02:AB and 02:AB:CD. The first octet must already be local unicast; values such as 02, 06, 0A and 0E are valid. Prefix 00 is rejected instead of silently changed. A local prefix does not designate a vendor.

Are the generated addresses unique?

They are checked for duplicates within the emitted batch. The tool does not check other batches, real devices or networks. It makes no global uniqueness claim. Repeated random draws are retried under a bounded draw budget; an exhausted budget returns an error without a partial batch.

What randomness source is used?

Generation runs in a browser worker using crypto.getRandomValues. There is no fallback to Math.random. If secure randomness is unavailable or throws an error, generation reports that it is unavailable. You can cancel an in-progress batch, and a ten-second timeout stops unexpectedly slow processing.

Do format or case changes generate new addresses?

No. Colon, hyphen, dotted and plain output, with uppercase or lowercase hex letters, represent the same six bytes. Changing the count or prefix clears the previous batch so a result cannot be mistaken for the new settings. Copy or download a batch before generating another.

Do copy and downloads include addresses beyond the preview page?

Yes. The preview shows up to 50 addresses per page, while Copy all addresses and CSV/TXT downloads include the complete batch of up to 10,000. CSV includes canonical hex and local/unicast flags. Import its address columns as text to preserve leading zeroes and prevent spreadsheet auto-formatting.

Is anything uploaded or saved?

No. Generation and formatting stay in your browser, and addresses are not automatically saved. Download the output before leaving. If clipboard access is blocked, download TXT for the complete batch or copy the visible preview page manually.

MAC Address Generator

Create synthetic MAC-address fixtures for test datasets. Generate a unique batch, optionally fix a local prefix, and switch between common text formats without changing the underlying addresses. Copy the complete list or download CSV and TXT.

Address countFixed local prefix (optional)

Generate 1–10,000 addresses. Leave the prefix empty, or fix one to three octets. Examples: 02, 02:AB, 02:AB:CD. A supplied prefix must already have its local bit set and multicast bit clear; it is never silently corrected.

Address formatHex letter case

Read the two address bits

Example first octet: 02

00000010

Bits shown from most significant on the left to least significant on the right.

U/L, bit 1 = 1: locally administered. This is not an IEEE-assigned vendor identity.

I/G, bit 0 = 0: individual / unicast, not multicast.

Without a prefix, the generator preserves the other six bits of a random first octet, sets bit 1 and clears bit 0. With a prefix, those fixed bytes are retained exactly. Remaining bytes come from crypto.getRandomValues.

What uniqueness means here

Duplicates are removed while generating a batch. This does not check other batches, devices or networks, and it does not establish ownership or vendor assignment.

Generation stops after a bounded number of random draws. A randomness failure or exhausted retry budget returns an error and emits no partial batch. Formatting and case changes do not draw new addresses. Count or prefix edits clear the previous batch; download it before changing those settings or leaving the page.

Synthetic local addresses only, not IEEE-assigned vendor identities or guaranteed unique on a real network. This page does not change device/network settings. Every generated address has local-bit 1 and multicast-bit 0; no globally unique or hardware-origin claim. Generation runs locally. Addresses are not uploaded or automatically saved.

Common questions

What kind of MAC addresses does this generate?: Six-byte, 48-bit EUI-style address fixtures with the locally administered bit set and the multicast bit clear. They are synthetic local unicast addresses, not hardware identities or IEEE-assigned vendor addresses. The tool does not change device or network settings.
What do the U/L and I/G bits mean?: In the first octet, bit 1 is the universal/local bit: this generator sets it to 1 for local administration. Bit 0 is the individual/group bit: it is cleared to 0 for unicast. Together, the first octet always satisfies (byte & 3) == 2. The other bits are random unless fixed by your prefix.
Which fixed prefixes are accepted?: Enter one to three complete hex octets, with no separator or a consistent colon or hyphen separator. Examples are 02, 02:AB and 02:AB:CD. The first octet must already be local unicast; values such as 02, 06, 0A and 0E are valid. Prefix 00 is rejected instead of silently changed. A local prefix does not designate a vendor.
Are the generated addresses unique?: They are checked for duplicates within the emitted batch. The tool does not check other batches, real devices or networks. It makes no global uniqueness claim. Repeated random draws are retried under a bounded draw budget; an exhausted budget returns an error without a partial batch.
What randomness source is used?: Generation runs in a browser worker using crypto.getRandomValues. There is no fallback to Math.random. If secure randomness is unavailable or throws an error, generation reports that it is unavailable. You can cancel an in-progress batch, and a ten-second timeout stops unexpectedly slow processing.
Do format or case changes generate new addresses?: No. Colon, hyphen, dotted and plain output, with uppercase or lowercase hex letters, represent the same six bytes. Changing the count or prefix clears the previous batch so a result cannot be mistaken for the new settings. Copy or download a batch before generating another.
Do copy and downloads include addresses beyond the preview page?: Yes. The preview shows up to 50 addresses per page, while Copy all addresses and CSV/TXT downloads include the complete batch of up to 10,000. CSV includes canonical hex and local/unicast flags. Import its address columns as text to preserve leading zeroes and prevent spreadsheet auto-formatting.
Is anything uploaded or saved?: No. Generation and formatting stay in your browser, and addresses are not automatically saved. Download the output before leaving. If clipboard access is blocked, download TXT for the complete batch or copy the visible preview page manually.