Japan’s mobile market remains intensely competitive, with four national carriers pursuing different priorities across speed, coverage and 5G deployment. New data from Ookla’s Speedtest Intelligence for Q3 2025 illustrates how those strategic choices shape everyday network use, especially as 5G expands beyond major cities.
According to the report, SoftBank delivered the highest median download speed across all network types at 62.05 Mbps, narrowly outpacing KDDI’s au at 57.85 Mbps. Rakuten Mobile and NTT DOCOMO followed with median download speeds of 53.54 Mbps and 50.50 Mbps respectively. SoftBank’s leading overall speeds reflect ongoing investment to boost performance and reliability in high-traffic areas, though that emphasis on throughput does not always produce broader 5G availability.
When isolating 5G performance, Rakuten Mobile recorded the fastest median 5G download speed in the quarter with 128.39 Mbps and median uploads of 22.34 Mbps, despite ranking third on combined median speeds. SoftBank was a close second on 5G with a median download of 127.45 Mbps and uploads of 17.51 Mbps.
High national coverage masks uneven 5G usage
Japan’s mobile market is highly saturated: early-2025 figures put cellular connections at about 194 million and a penetration rate of roughly 157%, shifting competition from subscriber acquisition toward service quality and access to next-generation networks. Government statistics indicate 5G population coverage reached 98.4% by the end of fiscal 2024.
Despite broad coverage, availability metrics reveal a gap between network footprint and user experience. 4G availability remains uniformly strong across operators, with scores above 97%, underlining how central LTE still is for nationwide service. By contrast, 5G availability—measuring how often users with 5G-capable devices are connected to 5G—varies significantly. NTT DOCOMO achieved the highest 5G availability at 38.4%, more than six percentage points ahead of au, while SoftBank logged the lowest 5G availability at 26.5%, even as it delivered the fastest median speeds overall.
These results illustrate a common trade-off: operators tend to concentrate 5G investment in dense urban cores with strong demand, while relying on extensive 4G coverage to serve rural and hard-to-reach areas.
Geography shapes 5G access across prefectures
Japan’s population is heavily urbanized, with over 92% of residents living in cities; at the same time, spectrum licenses require carriers to provide service across all 47 prefectures, including rural and mountainous zones. Ookla’s prefecture-level data show wide disparities in 5G availability. Osaka recorded the highest 5G availability at 35.2%, while Yamanashi ranked lowest at 9.1%—meaning users in Yamanashi were nearly four times less likely to connect to 5G than those in Osaka.
Prefectures with stronger 5G availability generally align with population and economic activity. Osaka, Tokyo, Aichi and Kanagawa posted robust results driven by targeted deployment in dense markets. Inland and mountainous prefectures such as Yamanashi and Nagano showed far lower 5G access, reflecting the higher costs and logistical challenges of extending 5G infrastructure to areas with fewer users.
These regional differences contribute to an expanding urban–rural divide: residents in less populated areas not only spend less time connected to 5G, but often experience lower speeds when they do connect.
Speed does not always follow access
Higher 5G availability frequently correlates with faster median speeds—Osaka combined 35.2% 5G availability with a median 5G download speed of 172 Mbps, and Tokyo showed 33.7% availability with median speeds of 128 Mbps. However, exceptions exist. Yamagata recorded the country’s fastest median 5G download speed at 181 Mbps despite a relatively low 5G availability of 13.9%. That pattern suggests that in some less congested areas, limited user density can yield high speeds for the few users connected to 5G, even though the network’s active use is limited.
Lower-end performance reveals quality gaps
Examining the 10th percentile of 5G download speeds—representing the slowest 10% of users—highlights where networks struggle at the lower end of performance. NTT DOCOMO often posted stronger minimum speeds in many prefectures, including a notable 41 Mbps result in Ishikawa, indicating more consistent baseline performance for disadvantaged users. SoftBank achieved the single highest 10th percentile result, recording 49 Mbps in Aomori, but its minimum speeds showed greater variance elsewhere, falling as low as 4 Mbps in Nagano and 6 Mbps in Chiba.
au and Rakuten Mobile tended to report lower but steadier minimum speeds, pointing to fewer extreme drops but less peak headroom. Urban prefectures typically exhibited narrower performance gaps between users, driven by higher site density and more uniform resource distribution.
Consistency improves where speeds are higher
Ookla’s 5G consistency scores demonstrate a clear link between speed and reliability. Prefectures with higher median 5G speeds were generally better able to support stable, everyday use cases such as video streaming. SoftBank recorded the highest consistency in several regions, notably Hokkaido and Tōhoku, while NTT DOCOMO and au showed steady consistency benefits from mature networks and ongoing upgrades. Lower consistency scores were more common in rural and geographically challenging areas, including parts of northern Kantō.
National progress, uneven local outcomes
Japan has achieved near-universal 5G population coverage through regulation and sustained investment, meeting broad national goals. Performance data, however, underscores clear differences in actual access and quality depending on location. Narrowing those gaps will require continued, targeted investment in prefectures and regions that remain harder to serve. Without focused efforts, uneven 5G experiences are likely to persist even as headline coverage figures remain high.
(Photo by Zac Gudakov)