Area Code 90 – Mobile Network

Overview of Japan’s +81 90 Mobile Prefix

The +81 90 prefix is a non-geographic mobile number range assigned to mobile network operators (MNOs) and mobile virtual network operators (MVNOs) in Japan. Unlike geographic area codes (e.g., 03 for Tokyo, 06 for Osaka), the 90 prefix does not correspond to a physical location; it is used exclusively for mobile services, enabling subscribers to retain their numbers when moving across the country. This prefix is one of the most recognizable mobile identifiers in Japan, alongside 80 and 70.

Technical Formatting and Dialing

Japanese mobile numbers using the 90 prefix follow the ITU-T E.164 international format: +81 90 XXXX XXXX, where the total number length is 11 digits after the country code (including the leading 0). In domestic format, the number is written as 090-XXXX-XXXX. The prefix is part of the National Significant Number (NSN), which includes the trunk prefix 0, the mobile identifier 90, and an 8-digit subscriber number.

When dialing from abroad, callers must replace the leading zero with Japan’s country code (+81). For example, a Japanese mobile number 090-1234-5678 would be dialed as +81 90 1234 5678 from outside Japan. From within Japan, callers simply dial 090-XXXX-XXXX (the leading 0 is retained).

Carrier Assignment and Number Portability

The 90 prefix is shared among major MNOs (e.g., NTT Docomo, KDDI/au, SoftBank) and numerous MVNOs. Since the introduction of Mobile Number Portability (MNP) in 2006, subscribers can switch carriers while keeping their 090 numbers. Consequently, the prefix no longer indicates a specific operator. For routing purposes, the network uses the full number to identify the current carrier.

International SMS and Voice Routing

For international SMS, messages sent to a 090 number should use the format +81 90 XXXX XXXX. Voice calls to these numbers are routed via international gateways and terminated on the Japanese mobile network. It is important to note that Japanese mobile numbers are not reachable via traditional landline prefixes; they are exclusively mobile.

Usage and Consumer Considerations

090 numbers are widely used for personal and business communications. They support voice, SMS, and mobile data services. For businesses, 090 numbers are often used for customer contact, but they are not toll-free; the caller may incur charges depending on their plan. When dialing from overseas, international tariffs apply. Some VoIP services and apps may offer reduced rates for calling Japanese mobiles, but the underlying routing remains the same.

In summary, the +81 90 prefix is a cornerstone of Japan’s mobile numbering plan, offering location-independent, portable numbers for millions of users. Understanding its format and dialing rules is essential for seamless communication with Japanese mobile subscribers.