Online live feeds of police scanners provide real-time information on disturbances and crime in the districts they cover. They inform local residents about potential dangers and demonstrate what sorts of calls police in the area receive.
A police scanner intercepts radio communication, most commonly between the dispatcher and patrol officers. Therefore, anyone listening to a scanner knows where and why an officer is being dispatched. Frequent listeners with knowledge of the local area can use this information to judge which areas are safer than others.
Scanners also demonstrate how police communicate and the codes they use. These "10 codes," which vary by jurisdiction, are police shorthand for crimes, acknowledgements and common events in police work. Scanner sites and applications commonly provide these codes, as they are necessary to understand what is being said.
While it is legal in every state to use a police scanner at home, it is illegal in five states to use one in a motor vehicle, and more states make it specifically illegal to use a scanner to help commit a crime.
Not all jurisdictions have available police scanners. In some areas, the police have chosen to encrypt their communications, making it impossible to listen in.