A contact tracing app is due to launch on Thursday after months of delay, technical issues and concerns about privacy.

The latest NHS Covid-19 app has been trialled on the Isle of Wight and in the London borough of Newham since mid-August, after an initial build was scrapped.

Here, we explain how the app is intended to work and answer other key questions.

How does the coronavirus contact tracing app technology work?

The app will rely on Bluetooth from your smartphone to keep a log of others who are also using the app whenever they are in close proximity to you.

It is able to do this by measuring the strength of the Bluetooth signal, as well as timing how long you were near each other.

To be considered a close contact, it general means having been within two metres of someone for 15 minutes or more, such as on a bus journey.

The app generates random codes every 15 minutes that are passed between phones, meaning identities are kept hidden.

Should a person present symptoms or come back with a positive test, the app will ask their permission to check your codes with other app users, distributing them via a central system.

If a code matches the log stored on a person's phone, it means they could have contracted the virus and will therefore be advised to self-isolate.

Will I be forced to install the app?

No, the app is voluntary.

Employers also do not have the power to force employees to install the app.

But surely it will be ineffective unless we're all using the app?

According to the NHS, all evidence shows that even at lower levels of use, the app can help slow the spread of the virus.

But the more people that use it, the more effective it will be.

Traditional human contact tracing will still be key to the NHS Test and Trace effort.

Is my location tracked?

No, the app does not seek permission to GPS features on your smartphone, meaning it is not able to track your movements.

The app only asks permission to use Bluetooth, which will need to be switched on at all times for it to work properly.

It also asks permission to use the camera - this is for the QR codes feature in the app, allowing people to check into places such as restaurants.

Do I need to provide any personal data?

Users will only be asked to provide the first part of their postcode, which is used to display the area risk level within the app.

The only time a person will be asked to identify themselves is if they request a coronavirus test.

 Which areas will the NHS Covid-19 app cover?

The app will only be available to residents in England and Wales.

Scotland and Northern Ireland have worked on their own apps.