MAC Address Generator

What is a MAC address?

A MAC address — Media Access Control address — is a 48-bit identifier burned into (or assigned to) every Ethernet and Wi-Fi network interface. It is the address Layer 2 of the network stack uses to deliver frames to a specific NIC on a local segment, before any IP routing happens. When your laptop joins a Wi-Fi network and gets handed a DHCP lease, the DHCP server is identifying your machine by its MAC; when a switch builds its forwarding table, it is mapping MACs to physical ports.

MAC addresses are six bytes, conventionally written as six pairs of hexadecimal digits separated by colons (aa:bb:cc:dd:ee:ff) or dashes (AA-BB-CC-DD-EE-FF). The first three bytes are the OUI — Organizationally Unique Identifier — assigned by the IEEE to a manufacturer; the remaining three bytes are the per-device serial chosen by that manufacturer.

How it works

Generating a MAC programmatically means producing 48 random bits with two flags set correctly in the first octet:

• Bit 0 (least significant) — I/G (Individual/Group). 0 = unicast (one NIC), 1 = multicast (a group). Random unicast MACs must leave this bit at 0.
• Bit 1 — U/L (Universal/Local). 0 = IEEE-administered OUI, 1 = locally administered. Random MACs set this to 1 so they don’t spoof a real vendor.

In random mode this tool generates six bytes from crypto.getRandomValues, masks the first octet to clear the I/G bit and set the U/L bit, then formats the result. In vendor mode it overwrites the first three bytes with a well-known IEEE-assigned OUI for the chosen vendor, leaves the last three bytes random, and clears the I/G bit. This produces addresses that look like they’re from that vendor — useful for testing inventory and fingerprinting code — but are not, in fact, registered.

Common use cases

• Lab and home-lab work. Setting up isolated test networks, building VLAN demos, learning how a switch’s CAM table works. Random MACs let you populate the lab without buying hardware.
• VM provisioning in test environments. Hypervisors normally assign MACs from their own pools, but for repeatable test fixtures it can help to pin specific addresses.
• Network code testing. DHCP server tests, ARP-table tests, 802.1X enrolment tests, NAC integration tests — anything that consumes a MAC as input and you want to vary it deterministically.
• Protocol fuzzing. Generating large numbers of distinct MACs to stress-test switch firmware, Wi-Fi controllers or DHCP pools.
• Documentation and screenshots. Plausible-looking but obviously-not-real addresses in tutorials, slide decks and product mockups.
• Privacy randomisation reference. Modern OSes (iOS, Android, Windows 10+, macOS Sequoia) randomise their Wi-Fi MAC per SSID to prevent cross-network tracking; this tool produces addresses in the same locally-administered space those OSes use.

How to use this MAC address generator

1. Choose mode: Random for fully synthetic addresses with the locally-administered bit set, or Vendor to use a well-known OUI prefix (Apple, Cisco, Intel, Microsoft Hyper-V, VMware, VirtualBox).
2. Pick a separator (colon, dash, dot, none) and case (upper or lower).
3. Set a bulk count between 1 and 100 if you need a list.
4. Click Generate. Each address is six independent random bytes (with the vendor or U/L override applied), formatted to your chosen style.
5. Use Copy to grab a single address or Copy all to take the full list, one per line.

Security considerations

MAC addresses are not secrets — they are broadcast in every Wi-Fi probe and Ethernet frame — but a few cautions apply:

• Don’t assume uniqueness. Random MACs from this tool are 6 random bytes; the birthday-paradox collision threshold is around 16 million addresses before two are expected to match. For typical test populations this is fine, but if you generate millions, check for duplicates.
• Don’t ship into production. As covered in the FAQ, these addresses are not IEEE-registered and could collide with real hardware on a real segment. Use your hypervisor’s MAC pool for production VMs.
• Vendor OUI mode is not impersonation-proof. Network gear can still detect that a device claiming an Apple OUI doesn’t behave like an Apple device (DHCP fingerprint, mDNS announcements, TCP window size). The OUI alone is not authentication; never use these to bypass MAC-based ACLs on a network you don’t own.
• MAC randomisation is a privacy feature, not a security one. It defeats passive cross-network tracking; it does not protect you against an attacker on your local segment.

Privacy

Each address is generated by crypto.getRandomValues on this tab. The vendor OUI table is shipped as a static JavaScript object — no API call is made. There is no upload, no logging, no analytics on the addresses you produce. After page load the tool works offline.

Compatibility notes

The output formats — colon, dash, dot and no-separator — cover every common consumer. Colon notation works with Linux ip, ifconfig, tcpdump, Wireshark filters, IETF RFCs and Cisco non-IOS tools. Dash notation is the Windows / IEEE 802 default that ipconfig /all and Hyper-V emit. Dot notation (aabb.ccdd.eeff) is the Cisco IOS native form. No-separator is what most programmatic interfaces (database columns, SNMP indices, RADIUS attributes) want. All four are the same 48-bit value rendered differently; conversion between them is mechanical.