The UK National Health Service has finally released its COVID-19 contact tracing app for iOS and Android, a full day ahead of its expected debut.

Based on the Exposure Notification framework created by Apple and Google, which leverages short-range Bluetooth tracking, the NHS COVID-19 app is available to residents of Wales and England. It doesn't collect any location data or personally identifiable information, plus everything is decentralised.

The app primarily will alert you when you cross paths with someone who has reported that they were diagnosed with COVID-19 - just like other Exposure Notification apps using Apple and Google's API. It has other features, as well, like the ability to scan QR codes to log visits at restaurants and stores.

NHS officials initially rejected Apple and Google's contact tracing framework because it stored data in a decentralised manner on a user's device. It forged ahead with creating its own system. Ultimately, however, the NHS decided to use Apple and Google's API. You can read the entire back-and-forth saga here.

The NHS COVID-19 app is free and now available in the Apple App Store and Google Play Store. It requires a device running iOS 13.5 or Android 6.0 or later.