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 number blocks is a battle against 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. Currently, the three blocks (090/080/070) provide approximately 270 million numbers in total, but with growing demand for IoT device numbering, the 060 block has also been formally added for mobile phones by a December 2024 amendment to Japan's numbering plan (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. There used to be correspondences like 090-1xxx for NTT Docomo and 090-3xxx for au, but these mappings have broken down as more users switch carriers while keeping their numbers. The Ministry's Telecommunications Number Designation Database shows the original allocation, but not the current carrier after MNP.
Mobile phone numbers qualify as personal information under Japan's Act on the Protection of Personal Information, so they 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.