The U.K. reportedly decided to go with a coronavirus contact-tracing application different from the system Apple and Google are creating jointly. The National Health Service built an app that creates a central database of people who have tested positive for COVID-19. The Apple and Google solution uses a decentralized system for privacy reasons.

Contact-tracing applications use a phone’s Bluetooth capabilities to detect if two people have been near each other for a set length of time. If one person is later found to have contracted COVID-19, then everyone they’ve been in near contact with going back days can be notified.

But there’s a significant difference between the NHS app and the system Apple/Google are developing as to who will contact the people who might have been exposed.

The NHS solution

The British health service’s digital innovation unit, NHSX, created a contact-tracing app with a centralized system that’ll allow the NHS to track the spread of the disease around the U.K. And after some waffling the government agency decided that’s the system it’s going to use, according to the BBC.

It’s the NHS centralized server that will notify people that they’ve been in contact with someone who tested positive for COVID-19. They’ll be told to get tested or go into quarantine.

The NHSX app has been criticized for draining the batteries of devices running it. iPhone apps aren‘t supposed to talk to each other in the background, without the user knowing about it. That’d make life too easy for hackers. But it is something of a roadblock for contact-tracing software.

But the agency now says they’ve solved the problem. “Engineers have met several core challenges for the app to meet public health needs and support detection of contact events sufficiently well, including when the app is in the background, without excessively affecting battery life,” a spokeswoman for NHSX told the BBC.

The Apple/Google alternative

The contact-tracing system Apple and Google are building will be decentralized. When someone using an application built on this system indicates they’ve caught COVID-19, their iPhone/Android will send out notifications to others that they’ve been in close contact with someone potentially spreading the coronavirus.

With no central listing of people who have the disease, neither the government nor hackers can easily track these individuals.

Another difference between this system and the U.K.’s is that Apple and Google are building contact-tracing APIs into iOS and Android, not writing a specific app. Governments and companies will be able to create their own apps using the APIs.

The system being created by Apple and Google will supposedly be ready for beta testing this week.

Many countries, many contact-tracing solutions

Germany is adopting the solution that’ll be built into iOS and Android. but the U.K. isn’t the only country going it alone.

Australia rolled its own app out on Sunday. Called COVIDSafe, this has already been downloaded almost 2 million times.

France is creating a contact-tracing system in-house too. But it’s run into the same limitations Apple places on Bluetooth access as the U.K.