What is the highest frequency commonly used for unlicensed radio connections?

The highest frequency commonly used for unlicensed radio connections is 2.4 GHz. This frequency band is used by a variety of devices, including Wi-Fi routers, cordless phones, and Bluetooth devices. It is also used by some microwave ovens. The 2.4 GHz band is unlicensed, which means that anyone can use it without having to obtain a license from the government.