eSIM for Japan from Portugal: How to Choose and Set It Up

Mobile data is one of the first things a visitor needs in Japan: maps, train times, translation and messages all depend on it. For travellers from Portugal, an eSIM is often the simplest way to get it, because you can buy it on your phone, install it at home and keep your Portuguese number in the same phone. This guide explains what an eSIM is, how to check that your phone can use one, when to buy and install it, what the plans look like, how to set up two lines without paying roaming charges by accident, the criteria for comparing providers, a checklist for arrival, troubleshooting, and the Japanese words you will see in your phone's settings.

What an eSIM is and when it helps in Japan

An eSIM is a SIM built into the phone as software. Instead of putting a small plastic card in a tray, you add a mobile plan by scanning a QR code, tapping a link or following an app. Apple describes it as a digital SIM that lets you activate a plan without a physical card, and a phone can usually hold several eSIM profiles and switch between them.

• You can set it up before you leave, on your home Wi-Fi, so you are online as soon as you land.
• There is no card to lose, no tiny tray to open and no queue at an airport counter.
• Your Portuguese SIM can stay in the phone, so your usual number keeps working for calls and text messages.
• It suits short trips, because tourist plans are sold by the day, week or month.
• It is less suitable if your phone does not support eSIM, if your phone is locked to one operator, or if you need a Japanese phone number for calls.

This post is only about eSIM. For pocket Wi-Fi routers and physical SIM cards, and how the three options compare, read our broader guide to internet and mobile data in Japan: SIM, eSIM and pocket Wi-Fi.

Check that your phone supports eSIM and is unlocked

• Look up your exact model in the maker's official eSIM list. Recent iPhones and many recent Pixel, Samsung and other Android phones support eSIM, but not every model and not every regional version does.
• Look in the phone's settings for an option such as Add eSIM, Add cellular plan or Add SIM. If the option exists, the phone supports eSIM.
• Check for a second identifier. Many phones show an EID, the eSIM's own identification number, in the About or General settings. If there is an EID, the hardware is there.
• Ask your Portuguese operator whether the phone is unlocked, which means it is not tied to that operator. Phones bought outright are usually unlocked, but phones sold with a contract or instalment plan may not be.
• If you have a work phone, check with your employer. Company devices are often managed or restricted.

The unlock question matters because a locked phone may refuse a plan from a different operator. Apple's guidance on using two plans says that if you want to use two operators, your operator must unlock the iPhone, or both plans must be from the same operator. Ask for this in writing or check in your operator's app before you pay for a Japanese eSIM, because you may not be able to get a refund after installing a plan.

When to buy and when to activate

• Buy a few days to a couple of weeks before you fly, so you have time to fix problems on home Wi-Fi. Do not leave it for the airport, where Wi-Fi is slow and you may have no data.
• Check the validity rules before you pay. Some plans start counting when you install them, others when the phone first connects to a Japanese network, and some have a deadline by which the eSIM must be installed, so read the provider's terms carefully.
• If the plan starts counting at installation, wait to install until the day before you fly or on the day. If it starts at first connection, you can install earlier and leave it switched off.
• Keep the confirmation email and the QR code. Many QR codes work only once, so take a screenshot of the instructions, not a second copy of the code to try again.
• Check the dates and time zone. A plan labelled seven days may count calendar days in Japan time, so a late flight can use up a day early.

Install before departure or activate on arrival

Data only, or voice and SMS as well

Tourist eSIMs for Japan are almost always data-only. They give you mobile data for apps, maps and messaging, but not a Japanese phone number for calls or text messages. A Japanese voice number requires ID verification and is rare among tourist eSIMs, which are almost always data-only. A few visitor voice plans exist, so check the conditions. For calls to hotels or restaurants in Japan, use an app such as WhatsApp or the hotel's own messaging, and keep your Portuguese line on for incoming calls and SMS from home. Check the provider's page for a statement like data only before you buy, and if a plan says it includes a number, read the conditions.

Typical allowances and validity

• Daily plans give a set amount per day, often one to three gigabytes a day, for a number of days. They suit heavy users, because the allowance renews each day.
• Total plans give a fixed amount, often in the range of five to twenty gigabytes, valid for seven to thirty days. They suit people who use data lightly and rely on hotel Wi-Fi.
• Unlimited plans exist, but read the fair-use rules. After a certain daily or total amount, speed may be throttled, which means slowed down, to the point where maps and video barely work.
• Validity is counted in days or in hours from activation. A 24-hour day can start from the moment of activation or at midnight, depending on the provider.
• These are typical ranges for planning, not offers. Plans change often, so check the current plan on the provider's own page.

A rough guide to how much you need: maps, train searches and messaging use little data, video calls and streaming use a lot, and photo backups in the background can use a surprising amount. If you are unsure, pick a plan you can top up or extend, and turn off automatic photo uploads while you are away.

Hotspot and tethering

Tethering, also called a personal hotspot, shares your phone's mobile data with a laptop or tablet. Some providers block it, limit it or allow it only on certain plans, and the rule is often in the small print. If you need to work from a laptop on the road, check the provider's terms for tethering or hotspot before you buy, and ask support if the page does not say. Remember that hotspot use drains your battery and uses data faster than phone use alone.

Keeping your Portuguese SIM active alongside the Japanese eSIM

Most modern phones can run two lines at once, which is called dual SIM. The usual setup for a trip from Portugal is simple: the Portuguese line handles calls and SMS, and the Japanese eSIM handles mobile data. Menu names differ by phone and by system version. The setup below is the common pattern, so adjust the wording for your phone.

• Label the two lines with clear names, such as PT and Japan, so you do not confuse them later.
• Set the Japanese eSIM as the mobile data line.
• Keep the Portuguese line switched on, so you can still receive calls and SMS, including verification codes from banks and apps.
• Turn data roaming off on the Portuguese line. This is the key step that prevents roaming charges.
• Turn data roaming on for the Japanese eSIM line only, because the eSIM uses Japanese networks that count as roaming for the phone.
• Leave the Portuguese number registered in WhatsApp. WhatsApp keeps working on the Portuguese number over the Japanese data, so your contacts do not need a new number.
• Turn off any option that lets the phone switch the data line automatically, such as allowing mobile data switching, because the phone may move data to the Portuguese line when it thinks the signal is better.

Apple's page on using two plans notes that automatic data switching does not work while data roaming is on for your current line, and that a voice-only line can lose features such as visual voicemail and MMS while the other line is using roaming data. Test your own phone, because behaviour differs by system version and by operator.

Avoiding accidental roaming charges

• Check that data roaming is off on the Portuguese line, not only on the whole phone. This is the most common mistake.
• Turn off Wi-Fi Assist (iPhone) or adaptive connectivity (Android). These features move traffic to mobile data when Wi-Fi is weak, which can quietly use the wrong line.
• Watch for apps that choose a line. Some apps, including messaging and navigation apps, pick the line themselves, so check which line each app uses in the phone's settings.
• Remember that calls and SMS on the Portuguese line while abroad can be charged by your operator. Ask your operator about roaming rates for calls and SMS in Japan, as Japan is outside the EU roaming rules.
• Check your Portuguese operator's roaming add-ons before you leave. Some operators sell daily or weekly bundles, but they are often more expensive than a local eSIM.
• Switch off voicemail and background cloud syncing on the Portuguese line if you do not need them.
• After landing, check the usage figures on both lines. A sudden increase on the Portuguese line is a warning.

Even careful travellers can get a surprise on a bill. If your phone is lost or stolen abroad, or you face an unexpected medical cost, read our guide to travel insurance for Japan and keep the emergency numbers and phrases saved offline, in case you cannot get a signal.

How to compare Japan travel eSIM providers

Well-known names for travel eSIMs in Japan include Ubigi, Airalo, Sakura Mobile, Mobal, Holafly and Nomad. We list them as examples only, without ranking them, because plans, networks and prices change often and each traveller's needs differ. We give no prices here: check each provider's own page on the day you buy. On 21 October 2026 we could open Airalo's Japan page, which named SoftBank as the main network, the Ubigi Japan page we tried did not open and we did not check the other providers, so we cannot confirm their details.

Setup checklist before and on arrival

• At home, on Wi-Fi: confirm the phone is unlocked and supports eSIM.
• At home, on Wi-Fi: buy the plan and read the start rule and the install deadline.
• At home, on Wi-Fi: install the eSIM using the QR code or the provider's app, and keep the instructions saved on the phone.
• Label the lines, for example PT and Japan.
• Set the Japanese eSIM as the mobile data line, and keep the Portuguese line for calls and SMS.
• Turn data roaming off on the Portuguese line, and on for the eSIM line only.
• Turn off Wi-Fi Assist (iPhone) or adaptive connectivity (Android) and automatic data switching.
• Take a screenshot of the instructions and the provider's support contact, and save them offline.
• On landing: take the phone off aeroplane mode, wait a minute and test a map or a web page.
• If the provider asks for an APN, enter exactly what it gives you. The APN is the access point name, a setting that tells the phone how to connect to the network, and most modern eSIMs set it automatically.
• Download offline maps and a translation language pack as a backup for places with no signal.

Troubleshooting

• No signal: turn aeroplane mode on and off, then restart the phone. Check that the eSIM line is switched on.
• Data does not work: check that the Japanese eSIM is selected as the data line, not the Portuguese one.
• Data does not work: check that data roaming is on for the eSIM line. This is the setting people forget most often.
• Slow data: it may be throttling after your daily or total allowance, so check the usage in the provider's app.
• The QR code says it has already been used: the code usually works once, so the profile may already be on the phone. Look in the phone's list of mobile plans before asking for a new code. If it is not there, contact the provider, as deleting an eSIM may mean it cannot be reinstalled.
• The phone says it cannot add the plan: the phone may be locked to an operator. Ask your Portuguese operator to unlock it.
• The eSIM was installed but the phone shows 圏外: wait a few minutes, check the network selection and try choosing the network manually.
• Still stuck: contact the provider's support through the app or email, and use the hotel Wi-Fi to do it.

Japanese words for your phone

Mobile data is only one part of getting around. For trains and buses, see our guide to IC transport cards in Japan: Suica, PASMO and ICOCA, which explains the cards you can use without any data at all.

Official information

We checked the following pages on 21 October 2026: Apple's eSIM support page, for what an eSIM is and how plans can be activated, Apple's page on using two plans on iPhone, for unlocking and data-roaming behaviour, and Airalo's Japan eSIM page, as an example of a provider page. We could not open Google's Pixel eSIM page on the day, so we do not cite it, and we cite no other provider. Plans, networks and prices change, so follow your provider's current instructions.