MAC-adressgenerator

(Dokumentation på engelska)

What it does

Generates random EUI-48 MAC addresses in your browser - one or a batch of up to 100. The tool generates on load and on every option change; Generate re-rolls the batch. Options sit in the left panel, the live list in a sticky right column with a count badge, copy, and a mac-addresses.txt download. Randomness comes from crypto.getRandomValues locally - nothing is transmitted. Every option is encoded in the URL, so a format you dialed in can be bookmarked or shared as a link.

How to use it

1. Pick a format - the separator control, or one of the quick-pick chips:

Preset	Shape	Where you see it
Colon, lowercase (default)	02:9f:1a:c4:b7:e8	Linux ip link, macOS ifconfig
Dash, uppercase	02-9F-1A-C4-B7-E8	Windows ipconfig /all, getmac
Dot, lowercase	02.9f.1a.c4.b7.e8	dotted octet pairs some switch CLIs print
No separator	029f1ac4b7e8	bare hex for configs, filters, and regexes

2. Optionally enter a 6-hex-digit OUI prefix such as aabbcc. Separators inside it are tolerated (aa-bb-cc works).
3. Set Count (1-100), toggle Uppercase or Locally administered as needed, and press Generate to re-roll.
4. Copy the list, download it as mac-addresses.txt, or share the URL - it carries your options (?sep=-&case=upper&n=10).

Examples

The deterministic examples below were produced with a fixed test sequence (octets 02 9f 1a c4 b7 e8), so they are exact:

• Locally administered, colon (the default): 02:9f:1a:c4:b7:e8
• Dash separator: 02-9f-1a-c4-b7-e8 - same address, different shape
• Dotted: 02.9f.1a.c4.b7.e8
• Bare: 029f1ac4b7e8
• Uppercase: 02:9F:1A:C4:B7:E8 - display only; the address is identical
• OUI aabbcc pinned: aa:bb:cc:02:9f:1a - your three octets, random rest
• OUI 001132 with Locally administered on: 02:11:32:02:9f:1a - the U/L bit is forced onto the vendor’s first octet
• The same OUI with it off: 00:11:32:02:9f:1a
• Malformed OUI (zz): shows Invalid OUI: OUI must be 6 hex digits, got "zz" and generates nothing
• A real run with the crypto RNG: 33:89:a4:f0:90:b6 - note the odd first octet (see below)

Good to know

A MAC address is 48 bits - six octets. The first three form the OUI (the vendor half, assigned by the IEEE); the last three are the device half. Two flag bits live in the first octet:

Bit	Mask	Name	When set
least significant	0x01	multicast	targets a group, not one interface
second-least significant	0x02	U/L	locally administered, not vendor-assigned

• Why locally administered is the default. A universal address belongs to real hardware; test data using real vendor OUIs can collide with machines on your network. Forcing the U/L bit marks the address as locally assigned - you keep the format, drop the vendor claim, and stop impersonating hardware. 02:9f:1a:c4:b7:e8 is exactly that: first octet 02 = U/L set, unicast.
• The U/L flag only touches the 0x02 bit. The multicast bit (0x01) is left alone, so a run can produce an odd first octet such as 33:89:…. Fine for test data and documentation; filter for an even first octet if you need guaranteed unicast.
• Uppercase is display only - 02:9f:1a and 02:9F:1A are the same address.
• Options live in the URL (sep, case=upper, oui, la=0, n); the generated values themselves do not - a shared link re-rolls fresh addresses for the recipient.
• Count caps at 100 per batch; press Generate again for more.
• Private: randomness comes from crypto.getRandomValues locally - never transmitted.
• Related tools: Random Port Generator,

  UUIDUUIDA 128-bit identifier generated to be practically unique without coordination, most commonly in version-4 (fully random) form.

  Generator.