Apple and Google have begun testing their joint contact tracing system, which will help public health authorities track the spread of COVID-19, the disease caused by the novel coronavirus. The two companies are releasing an early version, and it's called COVID-19 Exposure Notification in iOS.

More specifically, they're releasing an API - a set of building blocks and tools - to a small number of developers who are building apps for public health organisations. This API will help them integrate the COVID-19 Exposure Notification into their apps - plus they will be able to test it over the next several weeks. Apple and Google plan to release the API more broadly from mid-May.

To be clear, their COVID-19 Exposure Notification is essentially a phone-based contact tracing system. It uses your phone's Bluetooth signals, coupled with randomised tokens, to look for individuals who are within a few feet of you. Your phone logs those tokens, and if someone who is COVID-19-positive has crossed your path, an alert will be sent to your phone about the potential exposure.

Users will need to opt into this system, and everything will be anonymous. We talk about how the system works in this guide. 

Apple released a beta version of Xcode 11.5 and the third beta of iOS 13.5 on 29 April, which is what's enabling developers to incorporate the API into their apps. It also provides public health authorities with the code needed for their health apps. Google released similar updates for Android developers and public health authorities through Google Play Services and Android Developer Studio.

In the coming months, the COVID-19 Exposure Notification will also be built directly into iOS and Android, eliminating the need to use health apps.