Almost every question about data in Australia is really a question about distance. Sydney, Melbourne and Brisbane are straightforward. The problem is the 1,500 km between them and everything beyond.
The short answer about the outback
Large parts of inland Australia have no mobile signal at all. Not weak signal, not slow signal — no tower within range, from any network.
This is not something a plan can fix. A travel eSIM resells access to the Australian networks, so wherever Telstra, Optus and Vodafone have no infrastructure, neither do you. If someone sells you a plan promising coverage out there, they are either confused or lying.
Where it drops, concretely
- Stuart Highway (Darwin to Adelaide): coverage at the roadhouses and towns, long gaps between them. Hours of nothing is normal.
- Nullarbor Plain (Perth to Adelaide): the longest dead stretches in the country.
- Uluru and Kata Tjuta: the resort area has coverage. Out on the loop roads and walking tracks, not reliably.
- Great Ocean Road: mostly fine, with dips in the cuttings and behind headlands.
- Tasmania's west coast and highlands: patchy away from the main towns.
- Kakadu and the Kimberley: assume nothing outside the settlements.
Coverage along major routes generally follows the towns. If the map shows 300 km with no town name on it, expect 300 km with no bars.
What to actually do about it
Download offline maps for your whole route, not just the next leg. Google Maps and Maps.me both let you save regions. Do it on hotel wifi the night before.
Tell someone your route and your expected arrival. This is standard practice in Australia for a reason, and it matters more than any phone setting.
Do not treat a data plan as a safety device. If you are driving remote roads, the local advice is a satellite messenger or an EPIRB, and a car in good condition. That advice exists because phones do not work out there.
Fuel and water before the gap, not after it. You cannot look up the next roadhouse when you have no signal.
Which network your plan uses
Telstra has the widest reach outside the cities, and this is the one place in the world where that difference changes a trip rather than just a benchmark. Optus is good in populated areas and along major corridors. Vodafone is strongest in the cities.
Most travel plans do not let you choose. If your itinerary is city-and-coast, it genuinely does not matter. If you are going deep inland, read the plan page and see whether it names a network — and treat any gap in coverage as expected rather than as a fault.
How much data
Australia is a place where you use more data than in Asia, because public wifi is thinner and café wifi is often slower than you are used to.
- Cities and coastal towns, ordinary sightseeing: 2 GB per day.
- Long driving days with constant navigation and music streaming: 3 GB per day.
- Working from the road, or tethering a laptop: 5 GB per day or more, and check the plan allows hotspot sharing.
Note the irony of a road trip: the days you most want data are the days you cannot use any.
No Australian phone number
A travel eSIM is data only. In Australia this bites in a few specific places: car hire and accommodation often call rather than message, some parking apps want an Australian mobile number, and a few booking systems send confirmation by SMS.
Give your accommodation's phone number where a local contact is required, and use internet calling for anything you need to initiate.