How to choose an eSIM for Japan: what to compare before you buy

A mobile data plan is one of the first things to sort out before a trip to Japan, and the market for travel eSIMs is crowded. Plan names, data sizes, day counts and daily caps change every few months, and most comparison pages lean on the providers' own claims. So this page does not rank brands. It gives you a checklist to run any plan through, the alternatives to an eSIM and a way to decide how much data you need. For the wider picture on staying online abroad, see the connectivity guides.

If you use the checklist, you can compare any two plans in five minutes and tell which one fits your trip. Read each plan's own terms page, not the headline, because the details that cause trouble are in the small print.

1. Phone compatibility and unlock. The phone must support eSIM, and it must be unlocked by your home carrier. Check your phone maker's support page for your exact model, then ask your carrier whether the phone is unlocked. JNTO's own guidance on SIM cards says the phone must be unlocked to use a travel SIM, and the same logic applies to an eSIM: a locked phone can install the profile and then refuse to connect.

2. Data size and validity. Plans are sold as a fixed amount of data for a fixed number of days, as an unlimited plan in day blocks, or as a daily allowance. Match the size and the days to your trip, and read what happens when either runs out. Some plans expire when the days end even if data remains.

3. When the days start. Some plans count days from the install, others from the first connection in Japan. The difference matters if you install at home. Read the activation rule, and if it is unclear, install after you land.

4. Daily caps and slowdowns. An unlimited plan usually means full speed up to a daily cap and a slower speed after it. Check the cap level, the time the counter resets, and what slower means in practice. Maps and messaging work at low speeds, but photo uploads and video calls do not.

5. Hotspot rules. If you want to share the connection with a laptop or a partner's phone, confirm that tethering is allowed. Some plans block it, and regional plans block it more often than Japan-only plans.

6. The network behind the plan. Most travel eSIMs ride on a domestic mobile network, not their own. The network matters more than the brand on the app, especially away from the big cities. Look for the network name in the plan description, and for whether the plan can switch networks when one is weak.

7. Regional plans and routing. A plan that covers Japan and several other countries is handy for a two-country trip, but traffic may be routed through another country, which can add delay on video calls. For a Japan-only trip, a Japan plan avoids paying for countries you will not visit.

8. Phone number and calls. Many travel eSIMs are data-only. You can still use messaging and calling apps, and you should keep your home line on for texts from your bank. If you need a Japanese number, look for a plan that includes one.

9. Top-ups. Find out whether you can add data to the same plan, in what sizes and at what price relative to the original. Top-ups are often priced worse than the base plan, so buy the size you need at the start if you can.

10. Support and refunds. Check whether support is in English, whether it is available by chat, and what happens if the eSIM does not install or does not connect. Look for a refund or reissue policy before you pay, and for what happens if you delete the eSIM by mistake.

11. Price, relative to what you get. Compare the price per gigabyte and per day, not the headline price, and check the currency and any payment fee. A cheap small plan can cost more than a mid-size plan if you need a top-up.

The comparison table on this page compares plan types, not providers. It has no prices because prices change often and are only reliable on the provider's own page on the day you buy.

JNTO lists the main ways visitors get connected: free Wi-Fi spots, a rented pocket Wi-Fi router, and a travel SIM. It notes that many large hotels in cities offer Wi-Fi, but that traditional ryokan and smaller minshuku may not, especially in the mountains and rural areas, so check when you book. For a travel SIM, JNTO says major airports sell different data plans, and that electronics megastores such as Bic Camera and Yodobashi Camera also sell them. For a router, it says rental kiosks are at all major airports and you can reserve in advance and have the device delivered to your hotel.

An eSIM is the same idea as a travel SIM with no card: you scan a QR code and the plan installs on your phone. That is why it suits people who want to be online the moment they land. A physical SIM or a router suits people whose phone does not support eSIM, or who want one shared connection for a group.

JNTO's mobile guide describes a growing number of free Wi-Fi spots for visitors, marked with the Japan.Free Wi-Fi symbol, and lists carrier apps that give access to large hotspot networks. These help for downloading maps at a station or a cafe, but they require sign-up and the signal can be patchy, so they work as a backup, not a plan for a day of navigation. Do not rely on free Wi-Fi to buy a ticket or find your hotel on arrival.

Your home carrier's roaming day pass is the easiest option: no install, your normal number and the texts from your bank arrive as usual. For one or two days it can be fine. Over a week it often costs more than an eSIM, and speed varies by carrier, with some capping the speed after a small daily allowance. If your home plan already includes Japan, check the speed and daily limit in the small print, and you may not need anything else.

The size you need depends on what you do, not on the length of the trip. Rank your own habits from light to heavy. Maps and transit apps use a modest amount spread across the day. Messaging and email use very little. Uploading photos and video to the cloud uses much more, and so do video calls, streaming and a translation camera pointed at every menu. A laptop on a hotspot can use more than everything else combined.

Two settings save more data than any plan choice. Turn off automatic photo backup over mobile data before you land, and download offline maps for any rural area and for the cities you will use most. If you will work remotely or share a hotspot every day, look at an unlimited plan and read its cap. If your use is light and you will be on hotel Wi-Fi at night, a small fixed plan can be enough, and a top-up covers a bad day.

If your trip includes areas with patchy coverage, such as mountain trails, plan for it: save the route offline and tell someone your plan. The Kumano Kodo itinerary is a good example of a route where the tourism bureau advises carrying a paper map and a phone charger.

Install at home over Wi-Fi, label the new line "Japan" in your phone settings and leave it switched off. After landing, turn it on, set it as the line for mobile data and turn on data roaming for that line only. Roaming has to be on for most travel eSIMs to connect, even though you are not paying roaming rates. Leave your home line on for calls and texts, with its data roaming off.

If the eSIM shows signal but no data, check the APN, the access point name. Some plans fill it in automatically, and others need the value from the provider's install email. Keep that email offline on your phone, because you will need it at the moment you have no data.

The most common problem is not coverage but setup: an eSIM that shows full signal and loads nothing. Check three things in this order before you contact support. First, data roaming must be on for the travel line. Second, the phone must be using the travel line for mobile data, not the home line. Third, the APN should not be blank.

The second problem is a plan that stops mid-trip because the day count started earlier than expected. Read the activation rule before you install at home. If you run out of data at a bad moment, use free Wi-Fi at a station, hotel or cafe to buy a top-up.

If your home plan already includes Japan at full speed with a sensible daily allowance, you can skip this. A group of three or four who will always move together may spend less on one rented pocket Wi-Fi split between them, as long as someone owns the job of charging it each night and the group accepts that it cannot split up. Short stopovers are the other case: for a layover between an airport and a hotel with good Wi-Fi, free airport Wi-Fi and a carrier day pass can be enough.

Confirm that the phone is unlocked and supports eSIM. Pick two plans and compare them on the eleven points above. Check how the day count starts. Screenshot the QR code and the APN. Turn off photo backup over mobile data. Download offline maps for your cities and for any rural stretch. Keep your home line on for texts and set its data roaming to off. If you still cannot decide between two plans, choose the one with the clearer terms and the easier refund. Pair this with travel insurance and a plan for getting around, and you have covered the three things most travelers regret skipping.