The app will send you a notification if it calculates that your phone has been in close contact with the phone of someone who has tested positive for coronavirus. The alert is anonymous and will not identify the person in any way.
A scientific calculation, using an “algorithm”, has been developed by NHS doctors and scientists to work out which app users are ‘close contacts’. ‘Close contact’ means that your phone has been within 2 metres for 15 minutes or more with the phone of someone who has tested positive for coronavirus. Read more about how the risk-scoring algorithm works.
Based on the Bluetooth signal of your phone, the length of time near to another device, and the estimated level of infectiousness of the person at the time of the contact, the app is able to tell you if you've been close to someone who later tests positive, even if you do not know who that person is. For example, a stranger on a bus or someone you've stood close to in a long queue at the supermarket. Due to the data privacy-protecting features of the app, no personal data about you or any other app users can be accessed or shared. This means we cannot tell you who you've been in close contact with.
We strongly encourage people to follow the app’s advice to help to break chains of transmission and help to protect your loved ones and communities from coronavirus.