Twelve things to do before you fly

Why the order matters

Checking the handset comes before buying, because if it cannot take an eSIM nothing else matters. Installing comes before flying, because installation needs the internet you do not yet have on arrival.

What this checklist stores, and where

Every tick is saved to this browser only. There is no account, no sync across devices, and nothing is sent to a server. Clear the browser's data or open the list on a different device, and the progress resets — you start again from scratch.

Ticking off all twelve is a memory aid, not a guarantee that the trip will go smoothly. Ticking a box does not itself change whether your phone genuinely supports eSIM or whether the plan you bought actually covers the destination — those facts live on the device checker and the plan page, not in this list.

Confirm the handset properly before buying

Dialling *#06# and finding an EID is the technical check for eSIM support, but whether the phone is network-locked is a separate question entirely. A phone with an EID can still be locked, and an unlocked phone can still lack eSIM support altogether.

If you are unsure about a network lock, check directly with the original carrier or the shop the phone came from — that is information only they hold. Our device checker can only speak to eSIM support by model; it has no way to know the lock status of any particular handset.

Choosing a plan that covers the whole trip

If the trip touches several countries, including a layover where you intend to use data, check regional plans before buying one per country separately — a single plan sometimes covers the whole route more cheaply and without switching profiles.

But if a layover is not one where you plan to use data at all, there is no need to cover it. This genuinely depends on each traveller's itinerary — there is no single answer that fits every trip.

Installing at home the safe way

1. 1Open the email or order page holding the activation codeConfirm you can see the code or QR before starting, since the next step needs it.
2. 2Go into the phone's cellular or mobile network settingsThe menu name and location differ by brand and OS version — see the detailed step-by-step guide for the exact model.
3. 3Add a new cellular planLook for an option to add a plan or add an eSIM — the exact wording differs between operating systems.
4. 4Scan the QR code or enter the code manuallyIf scanning fails, use manual entry — most systems offer this option as a fallback.
5. 5Label the new line right awayName it something like 'Japan trip' so you do not switch the wrong line once you land.

Do this on Wi-Fi at home or at work, at least two days before flying, so there is time to fix anything that fails the first time. Waiting until the airport removes almost every option to fix a problem, since there is rarely time there, and some public Wi-Fi restricts certain kinds of connections.

Labelling lines and picking the data line

With two lines on the phone — the home SIM and the new eSIM — you must set explicitly which one carries data, or the phone may keep pulling data from the expensive-roaming home SIM without you noticing. Labelling the line during installation cuts the odds of picking the wrong one in an airport rush.

Turn off home roaming, but keep the line for OTPs

Switch off roaming data on the home SIM only, but do not disable the line entirely — you still need it for calls and bank verification texts, which most banks still send only to that number. Removing the SIM altogether risks missing an important OTP mid-trip.

Download offline content before, not en route

Offline maps of the destination city should be downloaded at home, since the first stretch after landing usually has no connection to fetch a large file. Keep key addresses or place names as a screenshot too, in case the map app is briefly unavailable.

When to start this checklist

At least two days before flying, so there is time to fix anything. But if you are unsure about a network lock or think you may need to contact the original carrier for an unlock, start well before that — dealing with the original carrier usually takes longer than expected.

If the phone fails item 1 or item 2

Not every model, and not every regional variant of the same model, supports eSIM, and a phone bought through certain carriers can be locked without the owner ever being told. If either check fails, confirm again with the device checker, then decide whether to borrow a backup phone or resolve the lock with the original carrier before travelling.

Travelling as a group or family

Each phone needs its own pass through this list, since the model and lock status can differ even within the same family. Even when the plan is to share one hotspot, the phone doing the sharing still has to go through the same check and install steps.

• A screenshot of the activation code or QR
• The SM-DP+ address saved as plain text, offline
• The order number
• Both support contact channels already saved on the phone

See install steps by device brand

Recheck the phone before buying

Contact us if a step will not complete

If installation fails or you are unsure whether a step genuinely passed, message us on LINE at https://lin.ee/skDPoNx (@esimonline), email esimonline.asia@gmail.com, or phone 089-942-0818 / 088-521-6848, with a screenshot of any error message. We take messages around the clock, every day.

Contact the team

A tick is a promise; a check is evidence

The boxes on this page read nothing from your phone. They are empty squares waiting for you to press them, so the whole list is only as reliable as you are at the moment you press one. Tick 'profile installed' because you remember tapping through something yesterday, and the list looks exactly as finished as it does for someone who just opened their settings and saw the line sitting there.

The fix is smaller than it sounds: replace remembering with looking. Every item on the list has at least one thing that visibly appears on screen when it is genuinely done. Tick only after you have seen it, and reading the list back at three in the morning becomes reading a record of what happened rather than a record of what you think happened last week.

A timetable from two weeks out to departure day

The twelve items were never meant to be done in one sitting the night before. The ones that can fail, and that take time to put right, belong early. The ones that take a minute belong last. Ordered that way, problems surface while you still have options rather than when all that is left is to live with them.

1. 1Around two weeks out: settle the handsetLook for an EID, and ask the original carrier about a network lock. These are the only items that, on failing, change the whole plan — borrowing a spare handset, or falling back to a physical SIM — so you want the answer as early as possible.
2. 2About a week out: choose and buy the planWalk the whole route country by country, including any layover where you intend to use data, then decide between per-country and regional. How much data is right depends on how you personally use a phone; there is no standard figure that fits everyone.
3. 3Two or three days out: install the profile on Wi-FiLeave yourself room for an install that does not take the first time. If you need to contact support, this is the window where an exchange still finishes before you leave.
4. 4The day before: accounts and offline filesDownload the maps, keep the boarding pass and the accommodation address openable with no connection, and confirm you can still get into the accounts that will ask you to identify yourself while you are away.
5. 5Departure morning: the last pass over the switchesRoaming data off on the home SIM, the eSIM line still present in the list, photo backup switched to Wi-Fi only. All of it takes a few minutes and none of it can fail in a way that needs a long fix.
6. 6After landing: bring it up in orderAeroplane mode off, eSIM line on, set as the data line, then give the phone a moment to register. The detail is in the first-hour section below.

When there is less than a day left

The timetable above assumes you have time. Trips decided at short notice are real, and the thing to sort out is which items are home-only and which can still happen at the airport or after landing. Anything that needs a connection you can trust has to happen before you leave the house, because after that you are relying on public Wi-Fi that nobody guarantees.

The most compressed order is: confirm the phone has an EID, buy a plan that covers the destination, install the profile on Wi-Fi, and save the activation code and SM-DP+ address somewhere you can open with no connection. Miss any of those four and the rest hardly matters. Downloading maps, switching photo backup to Wi-Fi only, and labelling the line can all be done at the gate if they have to be.

The one thing not to compress is the network-lock question. If the handset came on a carrier instalment plan or a contract with conditions, and you have no time to get a clear answer, carry a fallback — a physical SIM bought on arrival, for instance. Discovering a lock while standing in the arrivals hall is the hardest of all the problems this list exists to prevent.

Check the model before you buy

The accounts that will ask you to prove who you are

More trips get derailed by a login than by a slow connection. Banks, work email, the app you booked the hotel through — many of them ask for extra proof once they see you signing in from somewhere unfamiliar, and how they ask varies by provider. Some send a code by SMS, some use an authenticator app, some want you to open the bank's own app, which needs a connection.

The key point: the eSIM you bought supplies data, not your existing number. A code sent by SMS goes to the number on your home SIM. That is why the list says to switch off roaming data on the home SIM while leaving the line itself on. Switch the whole line off and the message never lands, and you will not find out until the moment you need it.

Whether SMS reaches you abroad depends on your existing carrier and its roaming arrangements in that country. We cannot answer that on your behalf for any particular bank. The only reliable route is to ask your carrier before travelling, and if the answer is vague, arrange a second way into the account that does not depend on SMS at all.

• Set up an authenticator app that generates codes with no signal, where the account supports one
• Keep the backup codes a service issues somewhere other than the phone — printed and tucked into the luggage, for instance
• Confirm you actually know the passwords to the important accounts, rather than relying on one device's autofill
• Ask the bank whether using the account from abroad involves any extra step, before you go
• Tell colleagues or family which channel is the one most likely to reach you while you are away

The files you must be able to open with no connection

The moment you most need information is the moment you have no connection: from stepping off the aircraft until the eSIM line finds a network — five minutes, sometimes longer. In that window an immigration officer may ask for your address, a driver may ask for the hotel name in the local script, and you may have to write the address on an arrival form. All of it happens before you can load a single page.

The most dependable approach is to turn the important things into still images on the phone. A screenshot always opens, whether or not the app behind it wants a fresh login, and there is nothing to load. The trade-off is that it will not update itself, so take them close to departure and retake them if a booking changes.

Aeroplane mode is the honest test. If it opens in aeroplane mode, it will open when you have no signal. If it does not, the thing still lives on a server rather than on your phone — a difference that is invisible while your home Wi-Fi is working.

Power: the plainest way to undo all this preparation

An eSIM lives inside the phone, not in your bag. When the battery dies you lose more than the internet: the boarding pass, the maps, the address, and every way of contacting anyone, all at once. Someone carrying a physical SIM can move it into a borrowed handset in an emergency; an eSIM profile stays with the device it was installed on. That difference is worth planning around before you leave.

Travel days drain a battery faster anyway: the phone hunts for networks wherever coverage is patchy, the screen is on more often, and a map left running while you walk costs more than an ordinary day spent sitting still. A charged power bank is not a luxury here; it is what keeps the rest of the list meaningful.

The first hour after the wheels touch down

The order on arrival matters as much as the order beforehand, because most people press several things at once while still standing in the aisle and conclude nothing works when the phone simply has not registered yet. One step at a time, each finished before the next, makes a real problem easy to tell apart from an impatient one.

1. Turn off aeroplane mode and leave the phone alone for a moment without pressing anything else
2. Switch the eSIM line on if it is off, and confirm it is the line you labelled
3. Set the eSIM line as the one carrying mobile data
4. Confirm roaming data on the home SIM is still off while the line itself stays on for messages
5. Wait for a local network name to appear, then try loading one page
6. If nothing appears, cycle aeroplane mode once, or restart the phone once

If all of that passes and there is still nothing, the next thing to look at is manual network selection, which some phones call carrier selection. Automatic suits most people, but choosing manually sometimes gets the phone attached faster. The name and location of that menu differ by brand and OS version.

Arrival-day symptoms and what they usually mean

Symptoms that look identical on screen usually have different causes, and telling them apart saves time because each is fixed somewhere else. The table below is a way of interrogating your own setup first, not a diagnosis that holds in every case — what actually happens depends on the handset, the local network, and the plan you are holding.

Long layovers deserve their own decision

Layovers are where decisions most often go wrong, because they sit halfway between travelling and arriving. A short one spent entirely airside may need nothing beyond the airport's own Wi-Fi. An overnight one, or a trip out of the terminal, or a connection likely to be rescheduled, is a different proposition — data in that country changes the whole day.

The first question is whether the plan you hold covers the layover country at all. A single-country plan for your destination will not work in the country you stop in, and whether a regional plan covers it depends entirely on that plan's own country list. Open the list on the plan page rather than inferring it from the region's name — what 'Asia' or 'Europe' includes is not the same from one plan to the next.

One more thing worth preparing for: plenty of airports gate their Wi-Fi behind a sign-in page that sends a code by SMS. If your home number cannot receive messages in that country, the free Wi-Fi in the list is not really available to you. It is another reason that knowing in advance where your existing number can receive SMS is worth more than most people assume.

Travelling with more than one device

One eSIM profile installs onto one device. If you carry both a phone and a tablet and want both online, you either buy separately for each or run one as a hotspot for the other. Which suits you depends on how heavily you use the second device and whether you need both at once.

If you go the hotspot route, two things are worth knowing first. Some plans permit tethering and some do not; the condition is stated in each plan's own details, so read it before buying if sharing is the point. And running a hotspot noticeably drains the host device — if that host is the phone holding your boarding pass and maps, you have hung everything on one battery.

A cellular watch is a separate check again: eSIM support on a watch depends on the model and is often tied to specific carriers, so not every profile can be installed on one. If you intend the watch to be independently online while you travel, confirm that model's limits with the manufacturer first.

Work trips and holidays rank the same items differently

The twelve items are the same; what you cannot afford to get wrong is not. Knowing which case you are in makes it faster to decide where the preparation time should go.

If the trip is for work

The expensive failure is missing a meeting or a deadline, so weight continuity over economy. That means budgeting more data than the arithmetic strictly requires, checking that the tools your team uses are reachable from the destination, and arranging a way into work accounts that does not rely on SMS alone. If large files have to go out, leave time as well — the speed you actually get depends on the local network at that moment.

If the trip is a holiday

The quiet consumers are automatic photo and video backup, and a map left running all day. Both are settled before departure, and doing so helps more than rationing once you are there. To get a rough sense of how much to buy, put your own habits into the calculator and read the result as a starting point rather than a verdict — everything it works from is your own estimate.

Estimate the data the trip needs

Fallbacks for when one item does not pass

A good list does not mean every item passes. It means you find out which one did not while there is still time to act. Three cases come up often enough to be worth planning for, and each has a different way out.

First, a handset with no EID, or one confirmed to be network-locked. The way out is to change which phone you travel with, borrow a spare, or plan on a physical SIM bought locally. All three are decisions to make before you fly; none of them can be completed in ten minutes at the airport.

Second, an install that will not complete. Retry on stable Wi-Fi and check the code was entered in full. If it still fails, contact the team with the order number and a screenshot of whatever message appeared. What does not help is hammering the retry button without reading the message, which usually says where the problem is.

Third, discovering late that the plan does not cover where you are going. Message the team straight away with the order number, and do not install the wrong profile in the meantime — an unused profile is easier to deal with. What can be changed or refunded depends on that plan's own policy, which the team will check against the actual order.

Keep the order record somewhere you can find it

When you do need help, what makes it quick is being able to say which order and which email address placed it. People who cannot find that end up digging through a mailbox on a connection that is not working yet — a situation entirely avoidable with one line written down in advance.

Hold three things somewhere that opens with no connection: the order number, the email address you ordered with, and a screenshot of the plan details showing which countries it covers and for how many days. The third earns its place beyond support conversations — it is what you go back to mid-trip when you cannot remember what the plan actually promised.

Closing the loop once you are home

The list ends at the gate, but a short set of tasks waits for you on the way back. Skipping them produces either a cost or a confusion the following week, and the most common one is forgetting to move the data line back to the home SIM and then wondering why nothing works at home when everything looks normal.

1. Switch the data line back to the home SIM
2. Turn off the trip's eSIM line so the phone does not switch to it on its own
3. Put photo backup back to the behaviour you actually want
4. Read how much data the trip really used and note it for the next decision
5. Decide whether to keep or delete the profile, after checking the plan's terms

That last one deserves a pause. A deleted profile usually cannot be reinstalled from the same code, so if days remain or the plan can be topped up, keeping it and simply switching the line off is the safer move. And the figure you noted in step four is the best input you will ever have for the next trip — better than anyone's average, because it came from your own habits under real travelling conditions.