Apple and Google have started to make their new, jointly-developed Exposure Notification technology available for public use. The technology automatically tracks which other phones your phones has been near for a certain period of time, using a new, Bluetooth-based system. When one user reports that they have tested positive for COVID-19, other users they have come into contact with are automatically alerted, so they can get tested. The system uses anonymous, frequently-changed tokens to preserve privacy. To use the system, users must install an official app from their local public health agency and explicitly opt in to the service. Apple and Google are only allowing one app per geographic region, and have multiple safeguards in place to protect user privacy, including a ban on collecting users' locations. The system is available now for public health agencies to develop and release their apps using the system, although not all governments plan to do so. It requires a new OS version to function. Apple released iOS 13.5 today, which includes Exposure Notification as well as other features specific to the ongoing pandemic. New versions of Android are expected soon that support Exposure Notifications. The two companies have promised a more comprehensive version of Exposure Notification in the coming months that will not require the installation of a special app, although it will remain opt-in.