GUIDE深度 · Deep dive
Country Codes and Calling Codes
There are two country-code sets: ISO alpha-2 (JP, CN, US) and alpha-3 (JPN, CHN, USA); ccTLDs are usually .jp/.cn/.us; calling codes are +81/+86/+1. Do not mix the three.
Three code types
ISO alpha-2: two letters, common in forms/domains.
ISO alpha-3: three letters, common in finance/aviation.
Calling code: +digits for dialing.
ccTLD
Usually matches the country code: .jp/.cn.
The UK uses .uk, not .gb.
FAQ
Is the US code +1?
Yes; Canada and parts of the Caribbean also use +1.
Memorize both?
Start with alpha-2, then add alpha-3 as needed.