What is eSIM?
eSIM - an electronic SIM or embedded SIM - is a rewritable SIM card that’s built into a cellular device like a smartphone or smartwatch. There's no need to pop open a slot or pry off a case to put in a SIM; an eSIM never leaves your phone. Instead, you simply download a "software SIM" for your provider of choice.
While eSIMs can help manufacturers cram more components into smaller spaces, the biggest winners are consumers. If and when eSIM goes mainstream, you'll essentially have the option to instantly change phone provider at any time (assuming you have locked yourself into a contract). You wouldn't even need to pick up a SIM card from a store or place an order online to port; you'd make the request from your device and voila, new telco.
If adopted widely, eSIM would almost certainly increase the ease of jumping from provider to provider. This would in turn increase competition, and could also help increase the visibility of smaller providers without a retail presence.
In Australia, the Apple Watch Series 3 is the only eSIM device you can buy, and as such, every telco's eSIM offering so far is focused around wearable technology and the ability to share a single number between multiple devices.
What devices support eSIM?
At present, the 4G enabled Apple Watch Series 3 is the only eSIM device only available in Australia. The Pixel 2 and Pixel 2XL are the first phones to feature an eSIM, but the embedded eSIM will initially only work with Google's Project Fi network in the United States.
Can I roam with an eSIM?
No Australian eSIM providers currently support international roaming.
eSIM on Telstra
Telstra's current eSIM product is called One Number. At present, it's only available to customers on postpaid plans. A Telstra spokesperson told us that it will also be available to prepaid customers "in the coming months".
Telstra will bill you an extra $5 per month to use One Number, but you'll get the first three months free.
Telstra MVNOs are currently unable to make use of One Number; you need to have a plan with Telstra directly.
"We are also exploring making [One Number] available to Telstra MVNO customers in the future, but there are no firm plans at this time," said a Telstra spokesperson.
eSIM on Optus
Optus' eSIM product is called Number Share. As with Telstra, it's only available on postpaid plans. Number Share is billed at $5 per month, and you'll get the first six months free.
Optus has yet to confirm whether Number Share will be available on any other plans or Optus-powered providers, but a spokesperson told us the telco is "committed to developing new technologies and is exploring how the Number Share capability could be extended to services offered by MVNO partners and Optus prepaid".
eSIM on Vodafone
Vodafone's eSIM product is called NumberSync. As is standard, you're only able to setup NumberSync if you're on a postpaid Vodafone plan. NumberSync is billed at $5 per month, but you'll get your first three months free if you sign up before December 31, 2018.
At present, Vodafone has no plans to offer NumberSync to prepaid customers or through Vodafone-powered MVNOs.
Setting up an Apple Watch eSIM
When you first pair a 4G Apple Watch Series 3 you'll be asked if you want to activate its eSIM (provided you're on a compatible plan). If you choose yes, you'll need to sign into your username and password for your provider, and confirm you want to add One Number (Telstra) or Number Share (Optus) to your plan. It's that simple.
If you've already setup your Apple Watch and didn't enable the eSIM, you can do so by opening the Watch app on your iPhone. Scroll down to "Mobile", and then tap "Set Up Mobile". Telstra and Optus will both send you a text to confirm that your eSIM is active.
Your 4G Apple Watch will only work on the same network as your iPhone.