New York State has launched COVID Alert NY, its official app enabling the COVID-19 Exposure Notification system developed by Apple and Google. New York is the largest US state to date to launch an app using the system, and joins ten other states that have already launched similar apps: Alabama, Arizona, Delaware, Nevada, New Jersey, North Carolina, North Dakota, Pennsylvania, Virginia, and Wyoming. New York's app supports the national key server that allows Exposure Notifications to work across state lines, including New Jersey, Pennsylvania, and Delaware. Exposure Notifications is an opt-in system that uses Bluetooth to track which phones come near which other phones, how closely, and for how long. When someone reports that they have tested positive for COVID-19, the service can alert other people that may have come into contact with that person, so they can get tested as well. The service does not track users' locations, and protects privacy by using randomly-generated, frequently-changed ID codes to keep everyone anonymous. The system is more effective the more people participate. New York's app is available now for Android and iOS. Several other states are working on similar apps they plan to launch soon, including California, Colorado, Maryland, Oregon, Washington, and Washington, DC. New York's app was developed by NearForm, which also developed Exposure Notification apps for New Jersey, Scotland, and Ireland.