New Zealanders planning to head to Australia when quarantine-free travel resumes will first need a crash course in how Australia's tracing system works.
New Zealanders and Australians will be able to travel freely between their respective countries from 19 April.
Use of the Covid-19 tracing app is mandatory in the hospitality sector across all of Australia and everyone is encouraged to use additional bluetooth tracing technology.
But each state has its own own rules as well.
Australia has a national-level Bluetooth app, Covid Safe, and every state has its own QR code scanning app.
Those apps are not compatible across state borders, Dr Andrew Chen from the Centre for Informed Futures at Auckland University explains.
"You can download multiple apps on to your phone. You'll have to use the right app in the right state.
Every state has its different rules on when scanning is mandatory, in addition to the requirement across the country for use of the tracing app in hospitality venues.
"New South Wales it's mandatory in hairdressers, in Western Australia it's mandatory in gyms and cinemas and churches, in South Australia it's mandatory for driving lessons, weddings and funerals," Chen said.
"Each place has their own list of locations that they consider to be high risk enough that scanning in is mandatory.
"If the customer does not check in they could be denied entry to the venue.
"If you do not have the app or you do not have a phone that is compatible or you don't have a phone at all then in most cases the venue should be able to check you in on your behalf."
Travellers might strike a few things they're not used to.
There are multiple QR code providers and some don't work with the state-based apps - as happened in New Zealand in the early stages of introducing the system.
"They haven't had the same rules that we have around all places being required to display the state QR code," Chen said.
"Most of the Australian state-level apps require an Australian phone number so we're not sure how they'll get around that for people coming in to New Zealand," he said, though he hoped that would be quickly changed.
Chen said the national tracer app provides push notifications to people who may have been in the same location as someone with Covid-19, but in the state-based system tracers will phone people.
If it's all starting to sound a bit complicated, Chen's advice is to take "newish" phone to Australia, if you have one, and talk to someone on the ground who knows the system.
Visitors to NZ
People arriving in New Zealand will be asked to download and use the NZ Covid Tracer app while in the country. There's no mechanism to make enforce this, just as downloading the app is not mandatory for people in New Zealand.
Chen said both New Zealanders and anyone travelling across borders needed to take part in contact tracing effort.
"As the travel bubble opens and more people come into New Zealand from overseas, it might be a low risk but it's not zero.
"So we all need to be on board with this here as well and make sure if somebody with Covid does end up in the country we can draw a circle around that case and their contacts quite quickly."
Information on Covid-19 in Australia and where to find local outbreak information is on the Australian Government Department of Health website.