Bali is the most popular destination for Roamly customers by a long way, and it's also where the "just buy a SIM at the airport" advice goes wrong most often. The queue at Ngurah Rai after a red-eye from Sydney, the "unlimited" packages that quietly throttle after 2GB, and the registration form in Bahasa are all avoidable.
This guide covers what actually matters for a Bali trip: which networks have coverage where you'll be, how much data a normal holiday uses, and what it costs against the alternatives.
The short version
Buy a travel eSIM before you fly and install it on Wi-Fi at home. You'll have data the moment you land.
A 10GB, 30-day Indonesia plan is A$19.45 and covers a normal one to two week trip for most people.
Telstra and Optus day passes work, but they cost A$5 to A$10 a day and add up fast on a 10-day holiday.
Keep your Australian SIM active for calls and texts, turn its data roaming off, and use the eSIM for everything else.
Coverage: where you'll be and what to expect
Bali's mobile coverage is better than most first-timers expect. The south of the island, from the airport up through Kuta, Seminyak and Canggu, is dense with towers and you'll see 4G everywhere and 5G in patches. Ubud and the surrounding villages are solid 4G. Uluwatu and the Bukit are fine in the built-up areas but drop to 3G on some cliff roads.
Where it gets patchy:
The Gili Islands and Nusa Penida. Coverage is usable but slower, and it depends heavily on which network your eSIM connects to. Expect 4G in the main strips and weak signal on the far sides.
Mount Batur at sunrise and the north coast. You'll get a signal at the top, but don't count on uploading video from the trail.
Inside villas with thick walls. Same as anywhere. Wi-Fi is your friend indoors.
Roamly's Indonesia plans connect to Telkomsel, XL, Indosat and Smartfren rather than a single small carrier, so you get the same towers as a local SIM. Telkomsel has the widest reach on the islands, and the eSIM will pick it up automatically where it's strongest.
What a Bali eSIM costs
Roamly's Indonesia plans at the time of writing:
3GB for 15 days: A$7.00
5GB for 30 days: A$12.45
10GB for 30 days: A$19.45
20GB for 30 days: A$25.45
50GB for 30 days: A$47.45
All plans are prepaid, data only, and reloadable if you run low. Prices are in Australian dollars with no surprise fees at checkout.
Versus carrier roaming
Telstra and Optus both sell international day passes. Check the current rate before you go, but they've sat around A$5 to A$10 a day for years, with a daily data allowance that most people blow through by mid-afternoon on a beach day. For a 10-day trip that's A$50 to A$100, and you're still on the same phone number and the same network selection your carrier chooses for you.
Roaming makes sense for a weekend, or if you genuinely need to make and receive normal phone calls on your Australian number. For anything longer, an eSIM wins on price and usually on speed too, because you're connecting directly to a local network rather than through your carrier's roaming agreement.
Versus the airport SIM
Airport SIMs in Bali are cheap in rupiah terms, but you're paying in time and hassle. You'll queue, hand over your passport for registration, and often end up with a "tourist" package that's throttled after a small amount of data. If your phone is eSIM-capable, there's no reason to do this anymore.
How much data you'll actually use
Bali holidays are data-heavier than people think because of three apps: Google Maps for scooter navigation, Instagram, and Grab or Gojek for rides and food. Add WhatsApp video calls home and you're at 1GB to 1.5GB a day without trying.
Light user (maps, messages, a bit of browsing): 3GB to 5GB for a week.
Normal user (Instagram, Grab, a few video calls): 10GB for a week or two.
Heavy user (streaming, working remotely, hotspotting a laptop): 20GB or more.
If you're not sure, go one size up. The price difference between 5GB and 10GB is A$7, which is less than a single day of carrier roaming.
Setting it up in five minutes
Check your phone supports eSIM. Most iPhones from the XS onwards and most recent Samsung and Pixel phones do. Your phone also needs to be carrier-unlocked.
Buy the plan on Roamly, then tap "Add to iPhone" or "Add to Android" from My eSIMs while you're on Wi-Fi at home.
Label the new line "Bali" so you can tell it apart from your Australian SIM.
When you land, set the eSIM as your mobile data line and turn on data roaming for that line only.
Turn data roaming off on your Australian line. Calls and texts still come through.
Your plan's validity starts when you first connect in Indonesia, not when you install, so installing a week early is fine.
Things that catch people out
Data roaming is off by default on the new line. If you land and have no data, this is the fix nine times out of ten.
iMessage and WhatsApp stay on your Australian number. Nothing changes there. The eSIM is just the data pipe.
Hotspotting works on Roamly plans, so you can share to a laptop or a travel companion's phone.
Don't delete the eSIM to "save space" until the trip is over. Once removed, it can't be reinstalled.
Ready to go? See Indonesia eSIM plans, or read our guide on how much data you need for a two-week trip.