Help

Getting started

Paste any text that contains MAC addresses (a switch MAC table, ARP output, DHCP leases, Wi-Fi controller exports, log files, even an email or spreadsheet) and click Find MACs. No cleanup needed: MACs are recognized in any common format, and details found on the same line (IP address, hostname, VLAN, interface) are pulled into the table too. Duplicate MACs are merged into a single row, and columns only appear when your data actually contains them.

Vendor names

Universally administered unicast MACs are matched against the official IEEE MAC assignment registries. A match identifies the registered prefix holder, which is useful evidence about the hardware but not proof of who made or operates a device. A few special cases get labels instead of a vendor: [special] Locally Administered Address covers local-unicast addresses, including randomized and manually configured addresses, and Unknown Vendor means no applicable registered prefix resolved, which can be worth a second look on a network you manage.

IEEE 802c divides local-unicast addresses into four SLAP quadrant bit patterns: x2 AAI, x6 reserved, xA ELI, and xE SAI. macs4days checks only an ELI address's exact first 24 bits against the Company ID registry. When one matches, the CID prefix registrant appears separately beneath the local-address classification. It identifies who registered that number range, not the address generator or hardware manufacturer; a randomized address can coincide with a registered CID prefix.

MAC format & case

Use the format buttons above the results to display MACs the way you need them: Base (AABBCCDDEEFF), Cisco (aabb.ccdd.eeff), Linux/Standard (AA:BB:CC:DD:EE:FF), or Windows (AA-BB-CC-DD-EE-FF). The A/a button switches between UPPER and lowercase. Everything you copy uses the format you've selected.

Copying results

The icon buttons above the table copy everything at once: all rows as CSV or JSON, just the unique MACs, IPs, or hostnames, only the MACs with unknown vendors, or a ready-to-paste Wireshark filter. Some buttons only show up when the results contain that kind of data. For a single device, open the ⋯ menu on its row to copy just that row, or its MAC in a specific format.

Sorting

Activate any column header by mouse or keyboard to sort the table by that column; activate it again to reverse the order.

Unparsed lines

Lines from your paste that didn't contain a MAC address are collected in the Unparsed Lines card, so you can double-check that nothing important was missed.

Local processing and offline access

Parsing and vendor lookups run in your browser. The vendor database is stored locally and refreshed automatically in the background when you're online, so lookups keep working without an internet connection. Results are copied or shared only when you choose an action that does so. You can also install macs4days as an app for quick access in the field.

Updates

macs4days quietly checks for new versions of the site while you're online. When one is available, a green icon appears in the title bar next to the theme buttons; its tooltip shows which version you're on and which is available. Click it to download and switch to the latest version in one step, no hard-refresh or cache clearing needed. The vendor database is separate and keeps itself up to date automatically.

Legal

© 2026 macs4days. The site and its results are provided "as is", without warranty or guarantee of any kind, express or implied, including accuracy, fitness for a particular purpose, and non-infringement. Use the output at your own risk and verify anything important independently. Prefix registrants come from the IEEE MA-L, MA-M, MA-S, IAB, and CID registries; CID registrants are displayed separately from hardware vendors. macs4days is not affiliated with or endorsed by IEEE, and registry data may lag or contain errors. Organization names are trademarks of their respective owners.