A mobile phone number is an 11-digit phone number starting with 090, 080, or 070. About 233 million mobile subscriptions were active in Japan as of the end of March 2026 (Telecommunications Carriers Association) - exceeding the total population - reflecting the growing trend of individuals holding multiple lines (work, personal, tablet, etc.). Beyond voice calls, mobile numbers are widely used for SMS verification, two-factor authentication, identity verification, and service registration, making them an indispensable means of personal identification in modern society.
The history of these number blocks is largely a history of responses to number exhaustion. In the early days of mobile phones, only 090 was available. As demand grew, the 080 block was added in 2002. In 2013, the 070 block was opened for mobile phones following the decline of PHS services. The three blocks (090/080/070) provide about 270 million numbers in total, and as of 2026 almost all of them have already been designated to carriers. In December 2024 the Ministry of Internal Affairs and Communications amended the numbering plan to add the 060 block for mobile phones: 11-digit numbers running from 060-1 to 060-9. The launch, originally planned for July 2026 onward, has been postponed and had not started as of August 2026.
With the spread of MNP (Mobile Number Portability), it is no longer possible to identify a carrier from just the first three digits. Because numbers are designated to carriers in blocks, the leading digits once offered a rough hint about which carrier a number had been assigned to. That inference no longer holds, since many users switch carriers while keeping their numbers. The designation lists published by the Ministry of Internal Affairs and Communications show which carrier a block was originally assigned to, but not which carrier a subscriber uses after an MNP transfer.
A mobile phone number is treated as personal information under Japan's Act on the Protection of Personal Information once it can be linked with other details, such as a name, to identify a specific individual, so it must be handled with care. If a number is leaked, risks increase for smishing (SMS fraud), SIM swap attacks, and nuisance calls. Effective countermeasures include not registering your number with unnecessary services, using authenticator apps instead of SMS for verification, and using a virtual phone number for service registrations. See Differences Between 090/080/070 Numbers for details on number blocks and Phone Number Privacy Tips for specific protective measures.