Phone data abroad: roaming, eSIMs and local SIMs compared

Everything here earned its place by changing an outcome. Nothing about mobile data while travelling is included to round the number up.

What each option actually is

Roaming uses your existing account on a partner network abroad, keeping your number, your calls and your messages working exactly as at home. A local SIM is a prepaid account with a network in the destination country, giving local rates and a local number. A travel eSIM is a data plan downloaded to a compatible phone, typically data only, activated without a physical card.

The right choice depends on whether you need your own number to keep working, which is the question most comparisons skip.

Your number is the hidden requirement

Bank verification codes, two-factor authentication, airline notifications and anyone trying to reach you all depend on your existing number. Removing your home SIM to insert a local one silently breaks all of that, which is discovered at the worst possible moment.

On a long trip, dual SIM handsets, or a phone that runs an eSIM alongside the physical SIM, solve this by keeping the home number active for texts while data runs on the cheaper plan. Where the phone supports only one, disabling data roaming while leaving the home SIM active is a workable compromise.

Cost structures differ sharply

Some home plans include roaming in certain regions at no extra cost, which makes them unbeatable within those regions and expensive outside them. Daily roaming passes charge a flat fee per day used, which suits short trips and becomes expensive on long ones. Local SIMs are usually cheapest per gigabyte and require buying, registering and topping up in a country whose language you may not read.

Travel eSIMs sit between the two on price and are the simplest to arrange before departure.

Compatibility and unlocking

ESIM support depends on the handset model and sometimes on the region it was sold in, and some carrier-supplied phones restrict it. A physical local SIM requires an unlocked phone, which is not universal, particularly on contract handsets.

Check both before departure, since resolving a locked phone from abroad is slow. Coverage also varies within a country, and the network with the best city coverage is not always the best rurally.

Registration and local rules

Many countries require identification to register a SIM, and some require a local address or a registration process that takes time. Airport kiosks are convenient and generally priced above the shops in town, though they handle registration for you.

Requirements change and differ by country, so check the current position for your destination rather than assuming. Keep the receipt and the registration details, since replacing a lost SIM usually requires them.

Practical resilience

Download offline maps, boarding passes and accommodation details before departure, since the gap between landing and connecting is where you need them most. Public wifi in airports and hotels is convenient and untrusted; anything involving banking is better done on mobile data or through a trusted connection. Set data limits and turn off background updates, since a single automatic backup can consume a travel data plan.

In practice, carry the means to charge, because a phone at two per cent is functionally the same as no connectivity at all.

Everything above, in order of what to do first

1. What each option actually is. Roaming uses your existing account on a partner network abroad, keeping your number, your calls and your messages working exactly as at home.
2. Your number is the hidden requirement. Bank verification codes, two-factor authentication, airline notifications and anyone trying to reach you all depend on your existing number.
3. Cost structures differ sharply. Some home plans include roaming in certain regions at no extra cost, which makes them unbeatable within those regions and expensive outside them.
4. Compatibility and unlocking. ESIM support depends on the handset model and sometimes on the region it was sold in, and some carrier-supplied phones restrict it.
5. Registration and local rules. Many countries require identification to register a SIM, and some require a local address or a registration process that takes time.
6. Practical resilience. Download offline maps, boarding passes and accommodation details before departure, since the gap between landing and connecting is where you need them most.

The takeaway

Decide first whether you need your own number to keep working. Everything else follows from that answer.

The trip goes better when the bag is boring.