Quick Answer
NTT DoCoMo is Japan’s largest mobile operator with 91.91 million subscribers, 70% 5G population coverage, and the best rural network. au by KDDI serves 71.46 million subscribers with the strongest urban 5G performance and au Hikari 1 Gbps fiber. DoCoMo has wider reach. au performs better in cities.
Side-by-Side Comparison
This table compares Japan’s two largest mobile operators on speed, coverage, and features.
| Feature | NTT DoCoMo | au (KDDI) |
|---|---|---|
| Subscribers | 91.91 million | 71.46 million |
| 5G Coverage | 70% population | Urban-focused |
| 5G Performance | Strong nationwide | Best in cities |
| Fiber Brand | FLET’S Hikari (via NTT) | au Hikari (1 Gbps) |
| Fiber Upgrade | 25 Gbps launching Tokyo (March 2026) | 1 Gbps standard |
| Language Support | Japanese primary | 13 languages |
| Strength | Rural coverage, scale | Urban 5G, multilingual |
Test NTT DoCoMo speed | Test au speed
Speed Comparison
au by KDDI delivers the best 5G speeds in Japanese cities. In dense urban areas like Tokyo, Osaka, and Nagoya, au’s 5G network consistently outperforms DoCoMo on download and upload throughput. KDDI has invested heavily in urban small-cell 5G deployment.
NTT DoCoMo has wider 5G coverage at 70% population reach. DoCoMo’s speeds are strong but spread across more territory. In rural areas, DoCoMo is the clear speed leader because au’s 5G often falls back to 4G LTE outside cities.
For fiber broadband, NTT is launching 25 Gbps FLET’S Hikari in Tokyo in March 2026. au Hikari offers a solid 1 Gbps connection. The NTT upgrade represents a generational leap in home broadband speed.
Run a speed test to measure your current connection.
Coverage
DoCoMo leads Japan on mobile coverage. Its 70% 5G population coverage is the highest among Japanese operators. Rural prefectures like Hokkaido, Tohoku, and Shikoku get better DoCoMo signal than au or SoftBank.
au by KDDI focuses 5G investment on profitable urban corridors. Tokyo, Osaka, Nagoya, and Fukuoka have dense au 5G networks. Coverage thins in rural Japan.
Both operators provide near-complete 4G LTE coverage across Japan. The coverage difference is mainly about 5G availability.
au stands out with 13-language customer support. Foreign residents and tourists in Japan benefit from au’s multilingual service, which is rare among Japanese carriers.
Which Should You Choose?
NTT DoCoMo fits users who travel across Japan or live outside major cities. The 70% 5G coverage and strong rural network mean consistent connectivity anywhere. The upcoming 25 Gbps fiber in Tokyo is a bonus for early adopters.
au by KDDI fits urban users who want the fastest 5G in cities. If you live and work in Tokyo, Osaka, or another major city, au’s urban network edge matters. The 13-language support also makes au the default choice for non-Japanese speakers.
Compare SoftBank as a third option, especially if you want the Y!mobile budget sub-brand.
Summary
DoCoMo wins on coverage (70% 5G, best rural) and scale (91.91M subs). au wins on urban 5G speed and multilingual support. Both are excellent networks by global standards. Your choice depends on whether you prioritize city speed or nationwide reach.
Test your connection at Kencang speed test and check the Japan internet overview for full market context.
Last Updated: March 28, 2026 Data Sources: TCA Japan subscriber data, Opensignal Japan report, operator announcements