Does My Router’s MAC Address Get Sent Online?

Generally speaking, the router's MAC address could be sent in app-specific payloads, especially for geolocation services. But if you're using a portable device, operating systems have restricted apps from accessing MAC addresses, so it's mainly a concern for desktop devices.

So just to clarify, is the MAC address only visible to the ISP and not to other websites?

Your device's MAC address actually gets stripped by your router. When your data packets are sent out, your router packs them and adds its own MAC address. The process continues through the network, so each time a packet passes through a router, it's passed along with the router's own MAC, concealing your original address from further hops.

Your ISP can see the MAC address of your router's WAN interface, but once your packets travel through another router within your ISP's infrastructure, that MAC address gets replaced as it moves beyond the physical link. So effectively, your router's MAC address won't be visible beyond your immediate network.

You might want to consider that WiFi geolocation services use your WAP's BSSID (which is often its MAC address) to approximate your location. While this isn't directly related to your question, it's an interesting aspect, especially if opt-in location services are used. However, routers will still strip the MAC address as they handle data packets.

Exactly! The MAC address is part of layer 2 networking, so it is only visible to devices on the same local network. As soon as it goes through a router, it's no longer sent out to the wider internet.