Japan's mobile networks explained for travellers: docomo, au, SoftBank and Rakuten

The four networks and their sub-brands

Japan has four operators that build their own mobile networks. As a visitor you mostly meet these names on eSIM plan pages or on your phone's status bar.

Rakuten Mobile has its own network but partly roams on au in some areas. For a visitor the sub-brands matter little; just know they are brands running on the same parent networks.

3G is gone: older phones and VoLTE

• au ended 3G on 31 March 2022.
• SoftBank ended 3G on 15 April 2024, and in Ishikawa on 31 July 2024.
• docomo ended its FOMA 3G service on 31 March 2026.

For a visitor this means a phone limited to 3G will not work at all, while most modern phones already use 4G and 5G. For a data-only eSIM, VoLTE is not the main issue, but if a plan includes calls or a Japanese number the phone needs VoLTE, because voice now runs over 4G or 5G.

5G in the cities

Large cities such as Tokyo, Osaka and Nagoya have 5G in many districts, but real speed depends on the district, the bands your phone supports and the plan's terms. Some plans stay on 4G. For maps, chat and video, 4G is enough, and you do not need 5G.

If the phone shows 5G but speeds feel the same, do not worry. In crowded districts such as Shinjuku or Shibuya, speed depends on how many people are online at that moment more than on the label on your screen. Also remember that battery drains faster when the phone keeps searching for 5G.

Coverage strengths and weak spots

• Strong: cities and most Shinkansen lines, including most tunnels.
• Weak: deep mountains, ski backcountry, remote islands and hiking trails.
• Worth knowing: city-focused trips rarely hit problems, but rural trips deserve a backup plan such as offline maps.

In practice, before hiking, climbing a mountain or visiting a small island, download offline maps and save key details on the phone, and do not assume there will be a signal all the way. Every operator is stronger in different areas, so none is best everywhere.

How travel eSIMs use these networks

Travel eSIMs usually ride on one or two of these networks. On a trip limited to Tokyo, Kyoto and Osaka the differences are small, but for Hokkaido, Tohoku, Kyushu's mountains or Okinawa's outer islands the network a plan uses matters more, so check which network a plan uses before you buy.

For a brand comparison read “Best eSIM for Japan 2026: brands and networks compared”, and for ski trips read “eSIM for Japan's ski season: Hokkaido and Nagano”.

How to see which network you are on

1. 1Look at the status barThe operator name usually appears at the top of the screen, for example NTT DOCOMO, KDDI or SoftBank.
2. 2Auf dem iPhoneGo to Settings, then Cellular or Mobile Data, and tap the eSIM line to see the carrier name and status.
3. 3Bei AndroidMenus vary by model, but it is usually under Settings, Network and internet, SIMs, or About phone, SIM status.

The name on the screen may belong to the operator that owns the spectrum rather than the brand that sold you the plan, which is normal. If the network name changes as you travel between areas, the plan supports several networks and the phone is choosing automatically.

APN and roaming basics

• Set the eSIM as the line for mobile data and turn on Data Roaming for that line.
• Switch off data on the Thai SIM but keep the line on to receive bank OTP texts.
• The APN is usually set automatically. If there is no data, enter only the APN values your plan provider gives you; do not guess.
• If it still does not connect, toggle airplane mode or restart the phone.
• Tethering depends on the plan, so check its terms first.

When something goes wrong, check first that Data Roaming is on for the eSIM line, then that the eSIM is the data line, and look at the APN last, because most problems come from the first two.

In short, check three things before flying: the phone supports eSIM and 4G or 5G, the plan's network suits the areas you will visit, and Data Roaming is set up for the eSIM line.

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