On Windows, open Command Prompt and type `ipconfig`
On Windows, open Settings > Network & Internet > Wi-Fi or Ethernet > Properties
On Mac, open System Settings > Network and select your active connection
On Mac, open Terminal and type `ifconfig`
On Linux, open Terminal and type `ip addr`
On Linux, open Terminal and type `hostname -I`
On iPhone, open Settings > Wi-Fi and tap the connected network
On Android, open Settings > Network & internet > Wi-Fi and tap the connected network
To check your public IP address, search `what is my IP` in a web browser
To check your router IP address, open your network details and look for the default gateway