Internet access on your phone depends on either cellular data access or a WiFi connection. A tablet or computer will also require WiFi access. WiFi is often available for free (even on Shinkansen), although it may sometimes be accompanied by somewhat annoying “captive portals.” Speeds on such free WiFi networks vary!

If your home cellular plan or subscription does not include roaming to foreign countries, you will not have cell phone reception in Japan, nor will you have cellular data access. In other cases, your carrier may automatically detect an attempt to use these services abroad and automatically activate an “extended” plan.

One example is AT&T International Day Pass®. If, on any given day, you make a call or use cellular data (such as messaging), it will work, but AT&T will charge you $12 for that day. That can add up. Alternatively, you can activate an international calling option (currently unlimited for $15 per month per device).

You can also purchase an eSIM. You will need to verify that your phone supports eSIMs (most modern iPhones do; I am not familiar with Android phones) and is not carrier-locked. eSIMs can be purchased from various vendors and installed before travel, with automatic activation upon arrival. This will add a second line to your phone with data access throughout Japan.

A final option is to rent a mobile Wi-Fi hotspot. These are small battery-powered (and rechargeable) devices slightly larger than a credit card, and about 1/2” thick. They connect to cellular networks and provide a Wi-Fi hotspot you carry around. You configure one or more devices (iPhone + iPad, or multiple users in your party) to connect to it. The result is that your phone will use WiFi whenever the WiFi device has cellular connectivity (in Japan, this is most of the time), but will fall back on cellular data on the phone when the WiFi device is not present.

The importance of your number being active

Even if you do not need to make or receive calls, and you have WiFi or an eSIM for data, you may find that your messaging app does not work because your number is not active in Japan (assuming you did not purchase an option for that, or you have the primary (e)SIM disabled). Many people choose to work around this by using WhatsApp or some similar app for messaging, but there may still be a problem. If you need to access an application or website that requires receiving a secret code via SMS, and the site or app does not offer alternative authentication methods, it won’t work.

Secondary authentication through SMS secret codes is known to be an outdated and insecure approach. Yet, many institutions still rely on it, and rarely offer alternatives, such as unique authenticator (OTP) codes or passkeys.

If you must be able to receive or make phone calls using your existing number, you must either enable this or choose an automatic option. If you do not need to make or receive calls, you can avoid the extra charges.

Scenarios

1. You must be able to receive (and make) phone calls on your regular number. You must accept the carrier’s automatic option or activate a monthly option (which is likely cheaper). In the latter case, do not forget to deactivate upon your return: the carrier will happily continue to bill you monthly for it!
2. You do not need your number active, but you do want data access most of the time. You can rent a mobile WiFi hotspot.
3. You do not need your number active, but do want data access all of the time, and you also need data access when the hotspot is not present (or out of battery). You need to buy/install an eSIM.

If there are multiple people in your party, you may want option 3 for each phone because if you get separated, either by accident or by design, only a subset of the people will have access to the WiFi hotspot. Having an eSIM will still allow everybody to communicate.

You may plan to rent a WiFi hotspot, but you can generally only pick those up after customs and immigration, or maybe not even until you reach your hotel. Meanwhile, you will have no connectivity (unless you keep your primary eSIM active). Yet, you may need to access the Internet before then. One example is accessing your Visit Japan QR code. This is where the eSIM will help!

If you do rent a mobile WiFi hotspot, you will generally be provided with a pre-addressed envelope. On your last day, you put everything in the envelope, seal it, and drop it in any mailbox.

There are no mailboxes beyond immigration when leaving the country, so if you do decide to retain your device until you arrive at the airport, make sure you mail it before going through immigration!

What we did

We are AT&T users and did not want the automatic charges (which are too easy to accidentally activate every day), and we had not researched enough to discover the $15/month-per-phone option. We were renting a WiFi hotspot. We were OK with not having phone calls, but we still wanted data access, even without the WiFi device.

We installed an eSIM on each phone and used Airalo as our provider. You install their app, log in, purchase an eSIM that suits your needs (we used the 30-day 5GB ones), and set it up. As soon as you come into contact with relevant cellular signals (typically at the airport), this process is activated, and your period begins. These eSIMs can be “topped up” when necessary through the app. There are many other providers, but Airalo worked well for us.

To prevent accidental charges, we also went into the settings and explicitly disabled our primary eSIM just before landing (and re-enabled it just before landing back home). Over the course of three weeks, with a party of three adults, we consumed a little over 100 GB of data through the WiFi hotspot. Everybody stayed under the 5GB limit on our eSIM. Without this hotspot, we would have had to purchase bigger eSIM plans or top up. We received the WiFi hotspot as part of our travel arrangements, which included hotel pickup.

Because of this, I am unsure of the cost for comparison purposes.

How well did it work?

We had cellular connectivity from the moment of landing, which was very handy. We never had a moment where we felt our phones were useless. We had a Pupuru hotspot, which generally worked well. On long days, it would run out of battery, but we carried a portable battery pack for such cases. We also had MagSafe extension batteries for our phones, which some of us needed almost every day. The hotspot generally worked well, but we discovered that when traveling by train, particularly when frequently going through tunnels, connectivity would drop (although cellular connectivity would drop as well). This did not generally happen in the subway. They must have infrastructure to support that scenario.

On several days, the device ran out of battery. I suspect this would have happened with any brand. In particular, very long days, frequent cell coverage interruptions, or weak cell signals. With interruptions, the device frequently reconnects, and it does so at full radio strength. This consumes a fair amount of battery. Once connected, the transmit strength will be reduced to optimize battery use.

For these reasons, I strongly recommend carrying a portable battery pack. Our device uses a USB-C cable, but others may not. Therefore, research and ensure you have a battery pack that supports either USB-A or USB-C (adapters are also available). Better yet, have one with a sizable capacity and multiple ports so you can connect another device simultaneously if needed.

We were handed the Pupuru choice. There are many others. Some plans include data usage limits, and when those limits are exceeded, your speeds will be throttled (so you still retain access). You may want to investigate before deciding if you plan to use a lot of data. Other options, in no particular order, and without endorsing any:

• Ninja WiFi
• Japan Wireless
• Sukura Mobile