After trials, delays and re-thinks, on Thursday the NHS Covid-19 app was launched in England and Wales.
Many see this as an important step in fighting the pandemic - one of the first to download it was Professor Brian Cox who said “data is the key to controlling the virus until a vaccine becomes available”.
Some people with older iPhones are having problems because you need an iPhone 6S (released Sept 2015) or more recent model in order to be able to download the app.
That’s because the system requires you to have the phone operating system IOS 13.5 or later.
There could be other problems due to geography - with one phone user in Cumbria reporting that she can only download the Scottish version of the app.
Some people are saying they will not use the app due to privacy concerns.
The government will be pleased to have the support of celebrity physicist Prof Cox.
He said: “For those who have privacy concerns about the NHS Covid app, it uses Apple and Google’s API (application programming interface) not government’s.
"If you are a conspiracy theorist and don’t trust Apple and Google, remember you have installed their OS anyway so it makes no difference."
To download the NHS COVID-19 app via the Apple store, click here.
To download the NHS COVID-19 app via the Google Play store, click here.