Here's why: WiFi is just one of many radio frequencies all around us these days. Devices that use the same 2.4 GHz frequency range can hurt your internet speed. These include many microwaves, cordless phones, Bluetooth devices, TVs, wireless security systems, baby monitors, garage door openers, and more. Some of these generate short range interference that can affect your WiFi even when the device is turned off. Many newer routers support automatic band-switching, meaning they will detect and switch devices to a faster frequency, but if your router is more than a couple of years old, you will want to manually change to a 5 GHz connection whenever possible. You can read more about the difference between 2.4 GHz and 5 GHz, or find out how to manually change the wireless channel on your router to avoid congestion.