How could I get MAC address of my website visitor?

A host cannot determine from the MAC address of another host whether that host is on the same link (network segment) as the sending host, or it is on a network segment bridged to that network segment.

MAC is short for Media Access Control, where media refers to the local transmission media. A MAC address is not broadcast beyond the LAN of the device it is connected to, as it is locked in the internal network. Whereas source and destination IP-Addresses remain the same and are therefore used for long-distance routing decisions, the source and destination MAC addresses will indicate the next hop.

The MAC address stored in the packet changes on every hop of its journey. Due to that, the MAC address stored in the packets which are received by your server will be the MAC address of your point of presence’s router or the equipment of your ISP.

The only way to get the visitor's MAC address is to run code on his laptop, from the browser. There is no way to do it since it would be a breach of privacy or security.

There are several workarounds like running Active-X controls for Internet Explorer only or running XPCOM for Mozilla Firefox only. But these approaches require extension installation or a prompt from the user, so they wouldn't work for collecting all the visitors’ MAC addresses in background.