eSIMratDual SIM and DSDS
by RonyA dual SIM phone runs two lines at once: two physical cards, one physical plus an eSIM, or two eSIMs depending on the model. The standard mode is called DSDS (dual SIM dual standby): both lines ring, but only one carries data at a time. iPhones from the XS onwards, and most eSIM-capable Android phones, work this way.
Why it matters when travelling
This is THE flagship travel eSIM scenario: your home line stays in place for calls and texts (bank codes included), and the local eSIM takes the data. You remain reachable on your number while browsing at local rates, without ever touching your physical SIM card.
The setup that works: home line active but WITHOUT data roaming, travel eSIM selected for mobile data. Recent iPhones (13 and later) can even keep two eSIMs active in parallel, handy when your main line is already an eSIM.
The misconception
“With two active SIMs, I pay roaming on both.”
You do not: each line only bills what it carries. If data roaming is off on your home line, it only carries incoming texts (free almost everywhere) and the calls you choose to take. Data goes through the travel eSIM, at its plan's rate.
In practice, device by device
On iPhone
- Settings, Mobile Data: each line appears with its label (Primary, Travel…).
- Under Mobile Data, select the travel eSIM as the data line.
- In the main line's settings, switch off Data Roaming. Calls and texts keep coming through.
On Android
- Settings, Network & internet (or Connections), SIM cards: switch both lines on.
- Pick the travel eSIM for Mobile data, your usual line for default Calls and Texts.
- Switch off data roaming on the usual line, line by line.
What it changes when you compare
Dual SIM frees your choice of plan: no need to hunt for an eSIM with a home number or incoming calls, since yours handles that. The result: you can compare data-only eSIMs, the most numerous and the cheapest on the market, without sacrificing anything.
Compare eSIM plans by destination
The rat's tip: Label your lines as soon as you install them (Settings, the eSIM, Label): “Personal” and “Japan” speaks louder than “Secondary” and “Cellular” when you are setting up data on landing, half awake.
See also
Frequently asked questions
How many eSIMs can a phone store?
Between 5 and 20 stored profiles depending on the model, but only one or two ACTIVE lines at a time. So you can keep the eSIMs of several trips installed and only switch on the current one.
Can I use two eSIMs at once with no physical SIM?
Yes on recent models: iPhone 13 and later run two active eSIMs simultaneously, as do several high-end Android phones. iPhones sold in the United States since the iPhone 14 have no SIM tray at all.
Does dual SIM drain more battery?
Slightly: two lines on standby poll two networks. The gap is modest day to day; while travelling, simply switch off the unused line if you want to claw back a few percent.