The Three Options

Getting online abroad comes down to three choices, and the right answer depends less on price per gigabyte than on the shape of your trip. A fortnight across four countries and three months in one place have genuinely different best answers, and articles that declare a single overall winner are not being straight with you.

Carrier roaming

Your existing SIM keeps working abroad, billed by your home carrier under a roaming agreement — either a daily pass or a per-megabyte rate.

Nothing to set up before you fly
Your usual number keeps working for calls and SMS
One bill, from a company you can already ring

By far the most expensive per gigabyte
Daily passes charge for days you barely use
Per-megabyte rates outside a pass can be brutal
Bill shock is a real and common outcome

Travel eSIM

A data profile downloaded onto your phone over the internet, running on a local network in the country you are visiting, alongside your existing SIM.

Far cheaper per gigabyte than roaming
Installed before you travel, active on landing
Your normal number stays available on the other line
Regional and global plans cover multi-country trips

Needs an eSIM-capable, carrier-unlocked phone
Usually data-only, with no local voice number
Requires internet access to install the profile

Local SIM card

A prepaid SIM bought on arrival from a carrier in the country you are visiting, replacing your SIM in the phone.

Often the cheapest per gigabyte of all
Comes with a local voice number
Large domestic allowances

Costs you your travel time to buy
Registration and ID checks in many countries
Your own number is out of the phone unless it is dual-SIM
One country only, and useless the moment you cross a border

The Costs That Are Not on the Sticker

Comparing the advertised price per gigabyte will lead you to the wrong answer, because the largest costs in all three options are structural rather than per-gigabyte. These are the lines that actually decide the bill.

Roaming daily passes charge per calendar day

A pass typically bills for any day you use data at all, on the local clock. A flight landing at 23:40 and a taxi map lookup can consume two days of pass for twenty minutes of use.

Roaming often bills each line separately

A family of four on one account usually pays four daily passes, not one. This is where a week abroad quietly turns into a three-figure bill.

Local SIMs cost time, and time on a trip is expensive

Finding an official store, queueing, showing a passport and waiting for activation is commonly an hour or two of a short trip. That is a real cost even though it never appears on a bill.

Local SIM registration can fail outright

Several countries require a local address or restrict prepaid SIMs for foreigners. Arriving and discovering this is a bad time to find out.

Unused eSIM data usually expires

Most travel plans are valid for a fixed window. Buying a large plan for a short trip wastes the remainder — matching plan size to actual use matters more than the per-gigabyte headline.

Losing your own number costs more than data

Swapping out your SIM means bank codes and two-factor messages stop arriving. People discover this when a payment needs confirming and the code is going to a SIM in a hotel drawer.

Keeping Your Own Number Reachable

This is the part travellers underestimate. Your bank, your email and your work login all send codes to your normal number. Take that SIM out of the phone and those codes stop arriving — usually noticed at the worst possible moment, when a card payment abroad needs confirming.

An eSIM sidesteps this cleanly, and it is the strongest argument for one over a local SIM. The data profile occupies the second line while your physical SIM stays in the phone, registered for calls and SMS. Switch cellular data to the eSIM, switch roaming data off, and you get cheap data without going dark on your own number.

The configuration that works

Cellular data: the travel eSIM.
Data roaming on the eSIM line: on — it is a local network to your home carrier, and this is the switch people forget.
Data roaming on your home SIM: off. This is what prevents the surprise bill.
Calls and SMS: your home SIM, so verification codes still arrive.
Check the setting again after landing — some phones reset the data line on network change.

If you also need to make cheap voice calls while abroad, data plus a browser-based calling service is usually cheaper than any roaming voice rate — that is the approach covered in our guide for remote workers and digital nomads.

Side by Side

	Roaming	Travel eSIM	Local SIM
Cost per gigabyte	Highest	Low	Usually lowest
Set up before you fly	Nothing to do	Yes	No — on arrival
Keeps your usual number	Yes	Yes, on the other line	Only if dual-SIM
Includes a local voice number	No	Usually not	Yes
Works across several countries	Yes, at a price	Yes, on regional plans	No
Needs a compatible phone	No	Yes	No
ID or registration required	No	No	Often
Time cost on arrival	None	None	One to two hours

Rates vary by country and change often, so check the live plan for your destination rather than trusting a figure printed here — see eSIM data plans by country.

When Each One Genuinely Wins

A weekend city break

eSIM

Two or three days is where roaming passes are worst value per day and a local SIM costs more of your trip than it saves. A small eSIM plan installed at home is the clear winner.

A two-week multi-country trip

Regional eSIM

Crossing borders makes local SIMs useless and roaming expensive. One regional plan covering the whole itinerary avoids both problems.

Three months in one country

Local SIM

Over a long stay the per-gigabyte advantage and the local voice number outweigh an hour spent in a carrier shop. This is the case where a physical SIM still wins outright.

One overnight business trip

Roaming, possibly

For a single day, a roaming pass can genuinely be the cheapest option once you count your own time. This is the one scenario where doing nothing is defensible.

You need to be reachable on your normal number

eSIM alongside your SIM

Data on the eSIM, your usual number still registered for calls and codes on the physical SIM, with roaming data switched off. This is the configuration most travellers actually want.

An older phone with no eSIM support

Local SIM

If the hardware cannot take a profile, the choice is between a local SIM and expensive roaming. Buy the local SIM.

Will Your Phone Actually Do It?

Two conditions, and both must hold. The phone needs eSIM hardware, and it must not be locked to a carrier. A locked phone with perfect eSIM support will still refuse a third-party profile, which is the most common reason an eSIM purchase goes wrong.

Broadly supported

iPhone XS and later, including SE from the 2020 model
Google Pixel 3 and later
Samsung Galaxy S20 and later, plus recent Fold and Flip
Most flagship Android handsets from roughly 2020 onward
Recent iPad and cellular Apple Watch models

Check before buying a plan

Phones bought on contract are frequently carrier-locked
Some regional model variants ship without eSIM
Mid-range and budget handsets vary widely
A phone bought second-hand may still be locked

The quickest check is in the phone itself: if the cellular settings offer to add an eSIM or a second line, the hardware is there. Whether the carrier permits it is a separate question, and one worth resolving before you pay for a plan.

Setting One Up

1
Buy before you leave, on a connection you trust
Installing a profile needs internet. Doing it at home on wi-fi avoids the circular problem of needing data to get data.
2
Install the profile but leave it switched off
Most phones let you install now and enable later. The plan’s validity window usually starts when the line first connects, not when you buy.
3
Label the lines
Name them something like "Home" and "Travel". Every later setting refers to these labels, and unlabelled lines lead to switching the wrong one.
4
On landing, enable the travel line and set it as cellular data
Then turn data roaming off on your home line. Both steps matter; doing only the first still leaves the expensive line reachable.
5
Confirm it attached to a local network
The status bar should show a local carrier name on the travel line. If it does not, toggle the line off and on before assuming the plan is faulty.
6
Leave calls and SMS on your home number
So verification codes keep arriving. This is the whole advantage over a local SIM — do not undo it.

Mistakes to Avoid

Leaving roaming data switched on after installing an eSIM — the phone falls back to the expensive line the moment the eSIM has no signal.
Buying the eSIM after landing, when you need internet access to install the profile in the first place.
Buying a plan far larger than the trip needs, then losing the balance to expiry.
Removing your physical SIM instead of leaving it in place for calls and verification codes.
Assuming a carrier-locked phone will accept a third-party eSIM. It will not.
Deleting an eSIM profile to free a slot — most cannot be reinstalled afterwards.

The short version: for most trips under a month, an eSIM installed before departure with your physical SIM left in place is the right answer. Local SIMs win on long single-country stays. Roaming wins almost nowhere, except a single overnight where your time is worth more than the difference.

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