Every network card — in your phone, laptop, router or smart TV — carries a MAC address that is supposed to be unique in the world. The first three bytes of that address are an OUI, a prefix the IEEE hands out to hardware manufacturers. Look up those bytes and you can often tell who built a device on your network.
This tool normalises whatever you paste in, checks that it is a valid 12-hex-digit address, and matches the prefix against a built-in list of common manufacturers. It also flags locally administered addresses, which a device assigns to itself and which do not reveal a vendor.
What is a locally administered address? If the second hex digit is 2, 6, A or E, the device assigned its own address and the prefix is not a registered vendor.
Does it work offline? Yes — the vendor database is embedded, so lookups run entirely in your browser.
Is my data private? Yes, nothing you type leaves your device.