Free mobile hotspot apps may perform one or several functions, including searching for and displaying nearby open Wi-Fi hotspots or allowing a person to use the device as a Wi-Fi hotspot. Some mobile carriers offer hotspot-specific plans or may have restrictions against using a device as a hotspot.
Using a mobile phone as a hotspot is called tethering. Tethering can use high amounts of data quickly if used to serve many devices at once or to stream large media files such as movies. Using a free tethering app may be against a mobile carrier's service terms without purchasing a special plan designed to serve mobile hotspot needs. Most carriers also sell specially designed portable devices that function as hotspots.