Emergency alerts are used to warn the public of an impending natural or human-made disaster, extreme weather, active shooters, and other threatening emergencies that are current or emerging. Emergency alerts are sent by authorized government alerting authorities through different systems, including the Emergency Alert System (EAS), Wireless Emergency Alerts (WEAs), and NOAA Weather Radio. The types of alerts that can be sent include Presidential Alerts, Imminent Threat Alerts, Public Safety Alerts, and Americas Missing: Broadcast Emergency Response (AMBER) Alerts.

WEAs are short emergency messages sent by authorized federal, state, local, tribal, and territorial public alerting authorities through cell towers to any WEA-enabled mobile device in a locally targeted area. WEAs can be sent to mobile devices when individuals may be in harms way, without the need to download an app or subscribe to a service. The messages are designed to get the attention of the recipient with a unique sound and vibration repeated twice, and they are no more than 360 characters.

The Emergency Alert System (EAS) is a national public warning system that allows the President of the United States to address the nation within 10 minutes during a national emergency. State and local authorities may also use the system to deliver important emergency information such as weather. EAS participants, including radio and television broadcasters, cable systems, satellite radio and television providers, and wireline video providers, deliver state and local alerts on a voluntary basis, but they are required to deliver Presidential alerts.

In summary, emergency alerts are used to warn the public of an impending disaster or emergency, and they are sent through different systems, including the EAS and WEAs. The types of alerts that can be sent include Presidential Alerts, Imminent Threat Alerts, Public Safety Alerts, and AMBER Alerts.