The best way to see which devices are connected to your Wi-Fi (and find out their IP and MAC addresses) is to use the open-source tool Angry IP Scanner. It’s lightweight, runs on Windows, macOS, and Linux, and doesn’t even need to be installed. It’s a handy way to keep tabs on your home network.
Just enter an IP range, click Start, and let the scan do its thing. When the scan finishes up, right-click any detected device to open its Windows shares or connect via FTP. Angry IP Scanner also shows MAC addresses, which are unique strings of numbers and letters used to identify each device, and gives you several options for managing or exploring your network.
It’s a powerful tool, that’s for sure, which is why you should use it responsibly. Scanning networks that you don’t own or have permission to access may violate privacy or network policies.