The voluntary app, which comes after months of delay, uses Bluetooth to keep an anonymous log of people who a user has been close to - and sends alerts to those who have been in close contact with those who have tested positive for the virus.
More: All you need to know about the new coronavirus contact tracing app Health secretary Matt Hancock said the "vast majority" of people had the right software, adding that some may need to upgrade their phone's operating system.
It is free and available to download for over 16s in England and Wales.
(Pocket-lint) - 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.
Switching the NHS COVID-19 app to a decentralized architecture has allowed it to plug into coronavirus exposure notification APIs developed by Apple and Google - resolving technical problems related to device detection which caused problems for the earlier version of the app.
The app will then advise users to self-isolate if they have been in close contact with a confirmed case.
The app protects your privacy as it uses Apple and Google's proven Bluetooth technology, designed so that nobody will know who or where you are. Scotland has its own app, which has more than one million downloads, covering around a quarter of its adult population, and Northern Ireland's app has over 300,000 user. The app has been through "rigorous" United Kingdom trials in the Isle of Wight, Newham borough of London and among NHS volunteer responders, which are claimed to have been successful.
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"I would urge everyone in the communities we serve to download the app and also stick with existing safety measures - please wash your hands regularly, wear face masks or face coverings and stay two metres apart, especially indoors".
The app will help the NHS understand if the virus is spreading in a particular area, so local authorities can respond quickly to stop it spreading further and save lives.
The UK's major network operators, including Vodafone, Three, EE and O2, giffgaff, Tesco Mobile, Sky Mobile and Virgin Mobile have agreed to "zero-rate" data charges incurred by all in-app activity, meaning they will not be charged for using it.
Downloading the app will provide instructions on making sure notifications are enabled and the feature is functional.
It will alert you if you have been in "close contact" with someone who has been diagnosed with coronavirus, and will also alert others if you yourself receive a positive test result. The more people who download and use this app, the more it will help us to prevent the spread of COVID-19. "So if we don't speed up testing then the app is functionally useless".