This article describes three ways to check if someone is using your Wi-Fi network without your permission. You can do this by disconnecting your devices, using the network scanner app Fing, and viewing the router's admin logs.
How to see who is connected to your wifi router
If you’re fairly new to routers and home networking and you’re thinking “how can I tell if someone is using my wifi?” there’s a quick and easy way to check: disconnect your devices. Here’s what to do.
Go to each room in your house and disconnect any devices that connect to your WiFi.
Disable Wi-Fi on all portable devices, such as smartphones, tablets and laptops.
