The app — known in Japan as COCOA (COVID-19 Contact-Confirming Application) — uses Bluetooth to collect data when it comes into one-meter contact of another device for more than 15 minutes. If a person subsequently tells the app they have tested positive for COVID-19, it will scan two weeks’ worth of contact data and inform anyone who had been in close proximity to the patient. It doesn’t store any personal information like locations or phone numbers, in accordance with Apple and Google’s tracking platform.

Japan’s delay in launching the app has left some concerned about its effectiveness. According to the University of Oxford, this type of app needs to be used by 60 percent of the population to be useful. In countries that adopted contact-tracing apps early on, such as Singapore and Iceland, that figure stands at around just 40 percent. Integrating the technology with existing apps is also a no-go, due to Apple and Google’s stipulations. As Nikkei reports, "A concrete plan for disseminating the app has yet to take shape," a spokesperson for Japan's health ministry said.

Update (6/20): The app is now available for Android and iOS devices. Also, an earlier version of this article referred to the app as developed by Microsoft, that has been updated to clarify that Japan hired a team of engineers who also work for Microsoft.