If an app user tests positive for coronavirus, they can choose to share their result anonymously. The NHS will then send alerts to other app users who have spent time near them, or been in ‘close contact', over the last few days. These alerts will never identify an individual.

‘Close contact’ is based on an algorithm, but generally means you've been within 2 metres of someone with coronavirus for 15 minutes or more. Read more about how the risk scoring algorithm works.

App users identified as close contacts will get this alert within hours of the person getting a positive test result, and will get official NHS advice on what to do next.