A country code is a number used to identify the destination country when making international calls. Assigned to each country and territory by the ITU (International Telecommunication Union), Japan's country code is +81. In E.164 format, the leading 0 of the area code is omitted after +81 (e.g., 03-1234-5678 becomes +81-3-1234-5678).
Country codes are organized into geographic zones. Zone 1 is North America (US/Canada: +1), Zone 2 is Africa (+2xx), Zones 3-4 are Europe (UK: +44, France: +33, Germany: +49), Zone 5 is Latin America (Brazil: +55), Zone 6 is Southeast Asia/Oceania (Australia: +61), Zone 7 is Russia (+7), Zone 8 is East Asia (China: +86, South Korea: +82, Japan: +81), and Zone 9 is West/South Asia (India: +91). Country codes range from 1 to 3 digits, with countries having larger populations and higher call volumes tending to receive shorter codes.
From a nuisance call perspective, calls from unfamiliar country codes may be one-ring scams. Particular caution is needed for Zone 2 African countries (Guinea +224, Sierra Leone +232, Liberia +231, etc.) and Zone 6 Pacific Islands (Nauru +674, Tuvalu +688, etc.). These country codes are frequently exploited for International Revenue Share Fraud (IRSF), where calling back incurs high charges. Unless you have overseas contacts, it is safest not to return calls from unfamiliar numbers starting with +.
You'll use Japan's +81 when calling Japan from abroad or when registering phone numbers in international format. When signing up for web services, you may be asked to enter your number in international format (+81). Understanding phone number formatting rules makes converting between domestic and international formats smooth. Review how to use +81 in the Japan country code guide and how to handle suspicious calls in international phone scam techniques.